Ink, ink-jet recording process, recorded article, recording unit, ink cartridge, ink-jet recording apparatus fluorescence enhancing method and method of elongating life time of fluorescence

ABSTRACT

Disclosed herein is an ink comprising
         (i) first and second organic compounds which are incompatible with each other;   (ii) at least one of a compound exhibiting fluorescence properties and a coloring material exhibiting fluorescence properties; and   (iii) a liquid medium dissolving or dispersing the components (i) and (ii) therein.

This application is a division of application Ser. No. 09/923,417, filedAug. 8, 2001, now U.S. Pat. No. 6,676,734.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink, an ink-jet recording processusing such an ink, a recorded article obtained by such a recordingprocess and instruments using such an ink, and particularly to an inkwhich can enhance fluorescence intensity and provide a recorded articlegood in record quality including stability, reliability and coloringability to look at, an ink-jet recording process using such an ink, arecorded article obtained by the recording process, and instrumentsusing such an ink. The present invention also relates to a method ofenhancing fluorescence of a fluorescent colored portion of a recordedarticle comprising a recording medium and the colored portion providedthereon, and a method of elongating the life time of fluorescence.

2. Related Background Art

Various investigations and reports have heretofore been made on inks forwriting utensils and inks for ink-jet. In particular, in order toenhance the quality of recorded articles, including fluorescenceintensity and coloring ability, such various proposals as describedabove have been made. For example, proposals of coloring materials andthe like each having a novel structure, which are suitable for use ininks for the above-described use applications, proposals of inks using acoloring material (hereinafter referred to as “fluorescent coloringmaterial”) exhibiting fluorescence properties as a main coloringmaterial, and proposals as to the combined use of a fluorescent coloringmaterial as a coloring material for inks have been made. In particular,the proposals as to inks, which pay attention to the fluorescenceproperties of fluorescent coloring materials, include Japanese PatentApplication Laid-Open Nos. 8-151545, 9-132729, 10-193775, 10-298462 and10-298467, and Japanese Patent No. 233038, and novel recording processesand fluorescent coloring materials have been proposed therein.

In addition, the proposals as to the use of fluorescent coloringmaterials include Japanese Patent Application Laid-Open Nos. 5-293976,6-191143, 6-322307, 7-009755, 7-305013, 8-053639, 9-003375, 9-01294,9-137097, 9-137098, 9-137099, 9-165539, 9-241565, 9-255904, 9-286939,10-007962, 10-183043, 11-080639, 11-320921 and 2000-038529, and JapanesePatent No. 2995853.

In recent years, the use applications of fluorescent coloring materialshave not been limited to the mere formation of beautiful color imagesheretofore conducted, and there have been proposed, for example,technical development that fluorescence properties are imparted to anink, information such as characters, numerals, marks and/or bar codes isrecorded on a recording medium with such an ink, and the fluorescent inkis caused to emit light by irradiating the recording medium withultraviolet light having a proper wavelength, thereby imparting anotherinformation (for example, security information) than visibleinformation. Accordingly, there is room to widen the use applications ofinks exhibiting fluorescence properties in many fields, and there is astrong demand for development of inks which are stable, reliable, highin fluorescence intensity and excelling in coloring ability.

SUMMARY OF THE INVENTION

With respect to the coloring ability of an ink on a recording medium,however, only chromaticity (L*,a*,b*) that is used as a measure ofcolors has heretofore been considered. Even when a fluorescent colormaterial is used, design is also made according to the conventionalmeasure under the circumstances. Therefore, it has been hard to say thatthe fluorescence properties of the coloring material are fully utilized.More specifically, even in the above-described various proposals makinguse of the fluorescent coloring materials, in the standpoint of thecoloring ability of the coloring materials, the fluorescent coloringmaterials are used on the basis of only the viewpoint of (L*,a*,b*), notthe viewpoint of the fluorescence properties, or attention is paid tothe fluorescence properties of the coloring materials, but no attentionis paid to the color developing properties of fluorescence, in otherwords, the interfacial properties of the fluorescence. Therefore, suchproposals have not fully made the best use of the fluorescenceproperties of the coloring materials.

It is accordingly an object of the present invention to provide an inkwhich can provide a recorded article to the recorded portion of which,for example, fluorescence properties important for colors of the naturalkingdom are sufficiently imparted fully making good use of thefluorescence properties of the ink, and which the recorded article hashigh fluorescence intensity and is excellent in print quality includingcoloring ability, said ink being capable of enhancing the stability andreliability of the recorded article.

Another object of the present invention is to provide an ink-jetrecording process by which a recorded article having a fluorescentcolored portion having high fluorescence intensity can be formed simplyand stably.

A further object of the present invention is to provide a recordedarticle equipped with a colored portion having high fluorescenceintensity.

A still further object of the present invention is to provide a recordedarticle having a fluorescent colored portion the fluorescence intensityof which is hard to be deteriorated with time.

A yet still further object of the present invention is to provide anink-jet recording apparatus, an ink cartridge and a recording unit bywhich a recorded article having a fluorescent colored portion exhibitingexcellent fluorescence intensity can be stably provided.

A yet still further object of the present invention is to provide amethod of enhancing fluorescence of a fluorescent colored portion of arecorded article comprising a recording medium and the colored portionprovided thereon, and a method of elongating the life time offluorescence.

The above objects can be achieved by the present invention describedbelow.

According to an embodiment of the present invention, there is thusprovided an ink comprising

(i) first and second organic compounds which are incompatible with eachother;

(ii) at least one of a compound exhibiting fluorescence properties and acoloring material exhibiting fluorescence properties; and

(iii) a liquid medium dissolving or dispersing the components (i) and(ii) therein.

The ink may further have a compound having a vapor pressure of not lowerthan that of diechyleneglycol.

The ink may be used as an ink for ink-jet.

According to another embodiment of the present invention, there isprovided an ink-jet recording process, comprising the step of ejectingthe ink for ink-jet described above from an orifice in response torecording signals.

According to a further embodiment of the present invention, there isprovided a recorded article obtained by the ink-jet recording processdescribed above, wherein the fluorescence intensity of a recordedportion formed on wood-free paper has a proportional relationship to thewater content in the wood-free paper.

According to a still further embodiment of the present invention, thereis provided a recorded article having a colored portion exhibitingfluorescence properties on a recording medium, wherein the coloredportion contains at least one of a compound exhibiting fluorescenceproperties and a coloring material exhibiting fluorescence propertiesand has an interface between the outermost surface thereof and thesurface of the recording medium, on which incident light on the coloredportion from the outside is reflected.

According to a yet still further embodiment of the present invention,there is provided a recording unit comprising an ink containercontaining the ink for ink-jet described above and a head portion forejecting the ink.

According to a yet still further embodiment of the present invention,there is provided an ink cartridge comprising an ink containercontaining the ink for ink-jet described above.

According to a yet still further embodiment of the present invention,there is provided an ink-jet recording apparatus comprising an inkcontainer containing the ink for ink-jet described above and a headportion for ejecting the ink.

According to a yet still further embodiment of the present invention,there is provided a method of enhancing fluorescence of a fluorescentcolored portion of a recorded article comprising a recording medium andthe colored portion provided thereon, wherein the colored portion isformed by an ink-jet recording process comprising the step of applyingan ink to a recording medium by an ink-jet system, and an ink comprising

(i) first and second organic compounds which are incompatible with eachother;

(ii) at least one of a compound exhibiting fluorescence properties and acoloring material exhibiting fluorescence properties; and

(iii) a liquid medium dissolving or dispersing the components (i) and(ii) therein is used as said ink.

According to a yet still further embodiment of the present invention,there is provided a method of enhancing fluorescence of a fluorescentcolored portion of a recorded article comprising a recording medium andthe colored portion provided thereon, which comprises providing areflecting interface for incident light on the colored portion from theoutside between the outermost surface of the colored portion and thesurface of the recording medium at the colored portion.

According to a yet still further embodiment of the present invention,there is provided a method of elongating the life time of fluorescenceof a fluorescent colored portion of a recorded article comprising arecording medium and the colored portion provided thereon, wherein thecolored portion is formed by an ink-jet recording process comprising thestep of applying an ink to a recording medium by an ink-jet system, andan ink comprising

(i) first and second organic compounds which are incompatible with eachother;

(ii) a compound having a vapor pressure not lower than that ofdiethyleneglycol;

(iii) at least one of a compound exhibiting fluorescence properties anda coloring material exhibiting fluorescence properties; and

(iv) a liquid medium dissolving or dispersing the components (i), (ii)and (iii) therein is used as said ink.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a head of an ink-jetrecording apparatus.

FIG. 2 is a transverse cross-sectional view of the head of the ink-jetrecording apparatus.

FIG. 3 is a perspective view of the appearance of a multi-head which isan array of such heads as shown in FIG. 1.

FIG. 4 is a perspective view illustrating an exemplary ink-jet recordingapparatus.

FIG. 5 is a longitudinal cross-sectional view of an ink cartridge.

FIG. 6 is a perspective view illustrating an exemplary printing unit.

FIG. 7 illustrates the mechanism of coloring including fluorescenceintensity according to the present invention.

FIG. 8 illustrates the mechanism of coloring including fluorescenceintensity according to the present invention.

FIG. 9 illustrates the mechanism of coloring including fluorescenceintensity according to the present invention.

FIG. 10 illustrates the mechanism of coloring including fluorescenceintensity according to the present invention.

FIG. 11 illustrates the mechanism of coloring including fluorescenceintensity according to the present invention.

FIG. 12 illustrates the mechanism of coloring including fluorescenceintensity according to the present invention.

FIG. 13 is a schematic perspective view illustrating principal parts inan exemplary ink-jet printer capable of installing a liquid-ejectinghead.

FIG. 14 is a schematic perspective view illustrating an exemplaryink-jet cartridge equipped with the liquid-ejecting head.

FIG. 15 is a schematic perspective view typically illustrating principalparts of an exemplary liquid-ejecting head used in the ink-jet cartridgeshown in FIG. 14.

FIG. 16 is a conceptual view illustrating a part extracted from theexemplary liquid-ejecting head shown in FIG. 14.

FIG. 17 is an enlarged view illustrating a part of the ejection openingsshown in FIG. 16.

FIG. 18 typically illustrates a state that an ink has attached to theejection opening portion shown in FIG. 17.

FIG. 19 typically illustrates a principal part in FIG. 16.

FIG. 20 is a schematic cross-sectional view corresponding to a sectionalform taken along line 20—20 in FIG. 19 and illustrating an ejectingoperation of a liquid in the liquid-ejecting head with time togetherwith FIGS. 21 to 27.

FIG. 21 is a schematic cross-sectional view corresponding to a sectionalform taken along line 20—20 in FIG. 19 and illustrating an ejectingoperation of the liquid in the liquid-ejecting head with time togetherwith FIGS. 20 and 22 to 27.

FIG. 22 is a schematic cross-sectional view corresponding to a sectionalform taken along line 20—20 in FIG. 19 and illustrating an ejectingoperation of the liquid in the liquid-ejecting head with time togetherwith FIGS. 20, 21 and 23 to 27.

FIG. 23 is a schematic cross-sectional view corresponding to a sectionalform taken along line 20—20 in FIG. 19 in the liquid-ejecting head andillustrating an ejecting operation of the liquid in the liquid-ejectinghead with time together with FIGS. 20 to 22 and 24 to 27.

FIG. 24 is a schematic cross-sectional view corresponding to a sectionalform taken along line 20—20 in FIG. 19 and illustrating an ejectingoperation of the liquid in the liquid-ejecting head with time togetherwith FIGS. 20 to 23 and 25 to 27.

FIG. 25 is a schematic cross-sectional view corresponding to a sectionalform taken along line 20—20 in FIG. 19 and illustrating an ejectingoperation of the liquid in the liquid-ejecting head with time togetherwith FIGS. 20 to 24, 26 and 27.

FIG. 26 is a schematic cross-sectional view corresponding to a sectionalform taken along line 20—20 in FIG. 19 and illustrating an ejectingoperation of the liquid in the liquid-ejecting head with time togetherwith FIGS. 20 to 25 and 27.

FIG. 27 is a schematic cross-sectional view corresponding to a sectionalform taken along line 20—20 in FIG. 19 and illustrating an ejectingoperation of the liquid in the liquid-ejecting head with time togetherwith FIGS. 20 to 26.

FIG. 28 is a schematic perspective view of an ink-jet recordingapparatus which is an example of a liquid-ejecting apparatus to whichthe liquid-ejecting head according to the present invention can beinstalled and applied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will hereinafter be described in more detail bythe preferred embodiments of the invention.

First Embodiment

The ink according to the first embodiment of the present invention has afeature that the ink comprises

(i) first and second organic compounds which are incompatible with eachother;

(ii) at least one of a compound exhibiting fluorescence properties and acoloring material exhibiting fluorescence properties; and

(iii) a liquid medium dissolving or dispersing the components (i) and(ii) therein.

The mechanism that a recorded article good in stability and reliabilityand moreover good in coloring ability fully making good use of thefluorescence properties of the ink can be provided by the ink accordingto this embodiment will be first described.

The present inventors have considered a wide variety of mechanisms fordeveloping inks which can provide recorded articles good in stability,reliability and coloring ability and carried out an investigation andidentification as to a wide variety of coloring materials and inkcompositions. As a result, the inventors have been led to a new factthat when 2 compounds which are incompatible with each other are used ascomponents for an ink, the coloring ability of the resulting recordedarticle can be made good, thus leading to completion of the presentinvention.

More specifically, it has been found that when an ink comprising 2organic compounds which are incompatible with each other, a compoundexhibiting fluorescence and/or a coloring material exhibitingfluorescence, and a liquid medium dissolving or dispersing the twoorganic compounds, and the compound exhibiting fluorescence and/or thecoloring material exhibiting fluorescence therein is used, the qualityof the resulting recorded article, including fluorescence intensity andcoloring ability is improved when the ink is applied on to a recordingmedium, a recorded article good in stability and reliability isprovided, and particularly, such an ink exhibits good results when it isused for ink-jet recording. In addition, it has been found that from theviewpoint of the fluorescence intensity of the recorded article, the inkaccording to the present invention having the above-describedconstitution can markedly enhance the fluorescence intensity comparedwith a recorded article formed with the conventional fluorescent ink.

When a mechanism for an ink which can provide a recorded article good instability an reliability and moreover good in fluorescence intensity,coloring ability, etc. is considered, attention is generally paid to howto dissolve or disperse a coloring material uniformly and in a goodstate in the ink as a means for enhancing the fluorescence and coloringability of the recorded article. In other words, an investigation ismade as to how to do away with aggregation of coloring materialmolecules or dispersed particles in the ink to make the coloringmaterial molecules or dispersed particles small, for example, whetherthe absorbance of the ink can be enhanced and whether the absorbance canbe retained in a high state when consideration is made on the ink, andthe ink is designed. It is attempted to make the coloring materialmolecules or dispersed particles in the ink applied on to a recordingmedium hard to aggregate by making the design of the ink in such amanner, thereby making the coloring ability and fluorescence propertiesof the coloring material good.

On the other hand, with respect to recorded articles (prints) formed byapplying an ink on to recording media, the present inventors havecarried out again an investigation as to the state of the ink on therecording media, and a wide variety of recorded articles in the world,consideration has been conducted repeatedly. As a result, the inventorshave first paid attention to the facts that there is an interfacebetween a recording medium and an ink on the recording medium in anyrecorded article though it may not be sharp, and that the ink on therecording medium is present in a state that the ink has possessed aninterface with the atmosphere. Further, attention has been paid to thefacts that when recording is conducted on, for example, wood-free paper,the coloring ability of a coloring material to look at tends to bedeteriorated when the penetration of the ink is enhanced, and that whenrecording is conducted on a back coated film, or a recorded article islaminated thereon, the coloring ability of the coloring material to lookat is improved. From the facts described above, an investigation hasbeen made from the viewpoints of how to form the interfacial state ofthe ink to the atmosphere, in which the coloring ability of the coloringmaterial becomes good on the recording medium, after recording, and howto retain such a state, thus leading to completion of the presentinvention.

The present inventors consider that the ink according to this embodimentcan markedly enhance the fluorescence properties and coloring ability ofthe resulting recorded article by the following specific mechanism.

In the ink according to this embodiment, as illustrated in FIG. 7, theindividual components are present in a uniform state that they have beenfully dissolved or dispersed in the liquid medium in the state of theink. In FIG. 7, reference numeral 7000 designates an ink droplet beforeimpacted on a recording medium 7009. In the ink droplet, referencenumerals 7001 and 7003 indicate two organic compounds incompatible witheach other, 7005 at least one (hereinafter referred to as “coloringmaterial” merely) of a compound exhibiting fluorescence properties and acoloring material exhibiting fluorescence properties, and 7007 a liquidmedium dissolving or dispersing the organic compounds 7001, 7003, andthe coloring material 7005 therein. Reference numeral 7009 indicates arecording medium. When such an ink droplet 7000 is applied on therecording medium 7009 to conduct recording as illustrated in FIG. 8, apart (particularly, liquid medium 7007) of the ink components evaporatesinto the atmosphere or penetrates into the recording medium to diffuse,as illustrated in FIG. 9, whereby the constitution and compositionalratio of the ink on the recording medium are changed. As a result, thetwo organic compounds 7001 and 7003 incompatible with each other, whichhave been stably present in the state of the ink, undergo phaseseparation in a lamellar state on the recording medium to form aninterface by the ink components between the ink and the atmosphere asillustrated in FIG. 10. Therefore, a state as if a recorded article hasbeen laminated by the individuals of the ink components is created. FIG.11 typically expresses the state shown in FIG. 10 for simplifying it. Alayer indicated by the reference numeral 1101 in FIG. 11 contains theorganic compound 7003 and the coloring material 7005, while a layerindicated by the reference numeral 1103 contains the organic compound7001 and the coloring material 7005. The surface of the layer 1101 formsa gas-liquid interface 1105, and the layers 1101 and 1103 form aliquid-liquid interface 1107 between them. As a result, in the recordedarticle formed by the ink according to the present invention, the layer1101 having a stable thickness is formed by the development of theliquid-liquid interface 1107. Therefore, the reflection of light can beeffectively developed, and so coloring ability including fluorescenceintensity is made good, thereby becoming an effective means for markedlyenhancing the fluorescence properties and coloring ability of therecorded article.

According to the investigation by the present inventors, it has beenfound that when a surfactant is used as one of the two organic compoundsincompatible with each other, an image good in coloring abilityincluding fluorescence intensity can be provided. The present inventorsconsider that this is due to the fact that when the surfactant is used,a micelle layer (1201) of the surfactant is formed as a surface layercovering the layers 1101 and 1103, and the reflection of light can bemore effectively developed by this surface layer 1201, so that thecoloring ability including fluorescence intensity is made better.

According Lo a further investigation by the present inventors, it hasbeen found that water is preferably used as the liquid medium in orderthat the two organic compounds incompatible with each other are causedto coexist in a substantially uniform state in the ink. Morespecifically, when water is used as the liquid medium, a wider varietyof compounds may be used compared with other liquid media, so that notonly room for selection of constituent materials of the ink can bewidened, but also the quality of the resulting recorded article formedwith wood-free paper is hard to be deteriorated compared with inksmaking use of a non-aqueous liquid medium, and the liquid medium canalso be removed by penetration into the wood-free paper, and moreoverthe liquid medium is stable to evaporation. The use of water is hencepreferred even from this point of view.

The ink according to this embodiment is preferably used in recordingthat the ink is fed through a space as against a recording medium. Morespecifically, recording is conducted by bring the ink into contact withthe recording medium to pressurize it like a ball point pen, the ink ispushed into the recording medium to make the mechanism according to thepresent invention hard to develop.

The components and the like of the ink according to this embodiment thatthe excellent effects are achieved by the mechanism described above willhereinafter be described.

The two organic compounds incompatible with each other, which constitutethe ink according to this embodiment, mean those undergoing phaseseparation in a lamellar state like, for example, water and oil whenonly the organic compounds are mixed.

Specifically, in three components of the two organic compoundsincompatible with each other and water used as a solvent, the organiccompounds are dissolved in water as the solvent. When water as thesolvent is evaporated under an environment of, for example, 50° C.,however, the two organic compounds are separated from each other. Inparticular, when the two organic compounds are those undergoingliquid-liquid separation as water as the solvent is evaporated, themechanism according to this embodiment is easier to be developed.

The liquid medium for these organic compounds are selected from among awide variety of liquids in view of the combination of the two organiccompound in compatible with each other and its compatibility with theseorganic compounds. However, it is particularly preferred that the liquidmedium be determined to be water. The reasons for it include stabilityof the resulting ink, and besides problems of quality and the like whena non-aqueous liquid medium is used, which have been mentioned in theabove-described mechanism, and ease of selecting the two organiccompound compatible with each other.

The two organic compound in compatible with each other may be anycompounds so far as they undergo phase separation in a lamellar statelike, for example, water and oil when only the organic compounds aremixed, as described above. However, for example, those one of which hasa solubility parameter of at least 15 and the other of which has asolubility parameter of at most 13 are preferred. If the solubilityparameter values of both compounds are too close, they become liable tobe compatible with each other, and so the effects of the presentinvention may be hard to develop in some cases. Incidentally, thesolubility parameter values as shown herein are values determined inaccordance with the Fedors method.

One (first organic compound) of the two organic compound incompatiblewith each other preferably has a glycerol group. The glycerol group hasstrong hydrating force and is easy to serve as the compound on the waterside of “water and oil” shown in the above-described specific example ofthe phenomenon of the present invention. Among such compounds, sugaralcohols as monomers, such as glycerol, xylitol and erythritol, andsugar alcohols as dimers and trimers, such as glycerol and diglycerol.

Further, ethylene oxide, propylene oxide or combination thereof may beadded as substituents to the compounds mentioned above. Among these,those having at least 3 hydroxyl groups and those liquid at normaltemperature are particularly preferred. The content of these compoundsin the ink is preferably controlled to 1.0 to 30% by weight,particularly 5.0 to 20% by weight based on the total weight of the ink.However, the present invention is not limited thereto according to arecording medium used.

The other (second organic compound) of the two organic compoundsincompatible with each other will now be described. As a compoundcorresponding to the second organic compound against the first compounddescribed above, is preferably used, for example, a nonionic compound.This is due to the fact that the nonionic surfactant better develops theabove-described mechanism compared with surfactants having a polargroup.

The nonionic surfactant usable as the second organic compound preferablyundergoes no phase separation in a state of an aqueous solution from theaqueous solution, This is due to the fact that when an ink is preparedwith water as a liquid medium, the ink can be inhibited or preventedfrom becoming unstable. This apparently indicates that the nonionicsurfactant is preferably used in a state uniformly dissolved ordispersed in water. In particular, a nonionic surfactant, which forms astate of an emulsion in water, may preferably selected. It is furtherpreferred that the content of the nonionic surfactant in the ink beselected within a range sufficient to retain the emulsion state in thestate of the aqueous solution, since the fear of stability in the ink iseliminated.

Among the nonionic surfactants, those having an HLB of at most 13 maypreferably be used in this embodiment. In general, those having an HLBexceeding 13 become too hydrophilic. However, the use of the nonionicsurfactant having an HLB of at most 13 permits well developing theabove-described mechanism that the 2 organic compounds incompatible witheach other, which are components of the ink according to thisembodiment, undergo phase separation on the surface of a recordingmedium to form an interface by the ink components between the ink andthe atmosphere, thereby making the coloring ability includingfluorescence intensity good.

When that having a nature between water and oil, in other words, thathaving a cloud point is used as the surfactant, the coloring abilityincluding fluorescence properties is improved in the phase containingthe surfactant. This is considered to be attributable to the fact thatthe compound exhibiting fluorescence and/or the coloring materialexhibiting fluorescence is dissolved and/or dispersed in a substantiallymonomolecular state, which is the best state to the coloring abilityincluding fluorescence properties, in the phase containing thesurfactant, a supersaturated portion thereof is dissolved and/ordispersed in a phase incompatible with the surfactant, thereby welldeveloping the coloring ability including fluorescence properties.

The specific content of the nonionic surfactant in the ink according tothis embodiment is preferably controlled to at least 1% by weight, morepreferably 1 to 20% by weight based on the total weight of the ink. Whenthe content falls within this range, the above-described mechanism canbe better developed, and moreover balance of print quality, for example,balance between feathering, which is whisker-like blur, and fixingability or concentration can be prevented from being deteriorated.

Among the nonionic surfactants satisfying the above-describedrequirements, particularly preferable compounds include compoundsrepresented by the following general formula (I) and the followingcompounds (II) to (VII).

wherein A and B are, independently of each other, C_(n)H_(2n+1) (n beingan integer of 1 to 10), and X and Y are, independently of each other, aring-opening ethylene oxide unit and/or a ring-opening propylene oxideunit.

(R: long chain alkyl group of a fatty acid such as stearyl lauryl oleicgroups, n is an integer)

Among the nonionic surfactants represented by the general formula (I),compounds represented by the following general formula (VIII) areparticularly preferred.

wherein m and n are integers.

In the ink according to this embodiment, the compound exhibitingfluorescence properties and the coloring material exhibitingfluorescence properties, which are the component (ii) of the ink, willbe described. The effect by the above-described mechanism is fullydeveloped when a compound exhibiting fluorescence properties or afluorescent coloring material is used. Further, since the ink accordingto this embodiment tends to exhibit better results in an aqueous systemmaking use of water as the liquid medium by virtue of theabove-described reasons, it is preferred that water-soluble compoundsand coloring materials soluble in water or hydrophilic compounds andcoloring materials be used as the compound exhibiting fluorescenceproperties and fluorescent coloring material used in the ink accordingto this embodiment.

The water-soluble or hydrophilic compounds and coloring materialsexhibiting fluorescence properties as referred to in the presentinvention include, for example, compounds and coloring materials (forexample, dyes) soluble in water by themselves, and also compounds andcoloring materials which are hydrophobic in themselves, but madehydrophilic by treating the surfaces thereof and seem to be dissolved inwater by a method of emulsifying them in water, or the like. However, atechnique that a coloring material is dispersed by using a resin as adispersing agent, like pigment dispersion is not included. The reasonfor it is that this type of coloring material is hard to develop theeffect by the above-described mechanism, and moreover it may not be saidto be a very preferable selection from the viewpoint of reliability ofthe resulting ink. All the states of the compounds exhibitingfluorescence properties and fluorescent coloring materials in such aliquid medium as described above will hereinafter be represented as“dissolution” unless expressly noted.

As the compounds exhibiting fluorescence properties and fluorescentcoloring materials used, are particularly preferred those containing anyof the following atomic groups

Specific examples of the fluorescent coloring materials containing anyof such atomic groups as described above include the followingcompounds.

Color under Fluorescent Name of dye Structure daylight colorBrilliant-sulfoflavin FF(C.I. 56205)

Yellow Green toyellowish green Basic YellowHG(C.I. 46040)

Yellow Greenishyellow toyellow Eosine(C.I. 45380)

Red Yellow toorange Rhodamine 6G(C.I. 45160)

Red Yellow toorange Rhodamine B(C.I. 45170)

Pink Orange tored Name of Pigment Structure Lumogen LYellow

Lumogen LBrilliant Yellow

Lumogen LYellow Orange

Lumogen LRed Orange

As the compounds exhibiting fluorescence properties, may be used, forexample, fluorescent brightening agents commonly used.

The content of such the compounds exhibiting fluorescence propertiesand/or fluorescent coloring materials as mentioned above in the ink ispreferably controlled to at most 1.5% by weight, more preferably at most1.0% by weight. The compound exhibiting fluorescence properties and/orfluorescent coloring material has a nature that when its content in theink exceeds a certain value, the fluorescence intensity of the ink islowered (the phenomenon refers to as concentration quenching). For thisreason, the concentration quenching cannot be prevented by theabove-described mechanism if the concentration exceeds 1.5% by weight.When only the fluorescence properties are considered to be mostimportant, it is particularly preferred that the content be at most 0.5%by weight.

From the viewpoint of the stability of the ink, a monohydric alcohol mayalso be additionally used in combination in the ink according to thisembodiment. The monohydric alcohol has an effect to mix water with oillike, for example, dehydration of gasoline. This indicates that themonohydric alcohol is preferably used in combination in the ink from theviewpoint of the stability of the ink upon development of theabove-described mechanism. In addition, the monohydric alcohol has agood effect for evaporation and penetration into a recording medium whenthe resulting ink is applied to the recording medium. Therefore, themonohydric alcohol is useful for better developing the effect of thepresent invention. The content of the monohydric alcohol in the inkaccording to this embodiment is 0.1 to 20% by weight, preferably 0.5 to10% by weight based on the total weight of the ink. Specific examples ofthe monohydric alcohol usable as a component of the inks according tothis embodiment include ethanol, isopropanol and n-butanol.

A water-holding agent may also be used in combination in the inksaccording to this embodiment. As the water-holding agent, may bepreferably used a compound selected from urea and urea derivatives. Whenat least one selected from urea and urea derivatives is contained in theink, the stability of the ink is improved. More specifically, when thecompound selected from urea and urea derivatives is contained, themechanism that the two organic compounds incompatible with each other inthe ink undergo phase separation in a lamellar state is prevented frombeing developed at a gas-liquid interface in a state of an ink. Inaddition, the selected from urea and urea derivatives also has an effectas a solvent aid, and so the use of such a compound is also preferredfrom the viewpoint of stability of the ink.

When the recording medium is, for example, wood-free paper, the effectby the mechanism according to the present invention is easy to developdue to the water-holding ability of the wood-free paper. Morespecifically, it is expected that water is held in the recording medium,whereby the time when the ink components are released into the recordingmedium and the atmosphere can be slowed, and so the phase separation ofthe two organic compounds incompatible with each other in the lamellarstate is made with good results.

As the urea derivatives, compounds other than cyclic compounds arepreferred, and at least one selected from alkyl derivatives of urea andethylene oxide and/or propylene oxide adducts of urea, or a compoundsuitably selected from derived compounds modified by at least two of theabove derivative groups is preferably used. However, the selectionvaries according to the amounts and kinds of individual componentsmaking up the ink. That soluble in water is preferably used. Noparticular limitation is imposed on the amount of such a compound used.However, it is generally contained in a range of preferably from 0.1 to15% by weight, more preferably from 0.1 to 10% by weight based on thetotal weight of the ink.

In the inks according to this embodiment, may be contained variousadditives such as a water-soluble organic solvent, a surfactant, a rustpreventive, a preservative, a mildewproofing agent, an antioxidant,anti-reducing agent, an evaporation accelerator, a chelating agent, awater-soluble polymer and a pH adjustor, as needed,

As the liquid medium used in the inks according to this embodiment,water is preferably used as described above. More preferred is a mixtureof water and a water-soluble organic solvent. Specific examples of thewater-soluble organic solvent include amides such as dimethylformamideand dimethylacetamide; ketones such as acetone; ethers such astetrahydrofuran and dioxane; polyalkylene glycols such as polyethyleneglycol and polypropylene glycol; alkylene glycols the alkylene moiety ofwhich has 2 to 6 carbon atoms, such as ethylene glycol, propyleneglycol, butylene glycol, triethylene glycol, thiodiglycol, hexyleneglycol and diethylene glycol; 1,2,6-hexanetriol; glycerol; lower alkylethers of polyhydric alcohols, such as ethylene glycol monomethyl (ormonoethyl) ether, diethylene glycol monomethyl (or monoethyl) ether andtriethylene glycol monomethyl (or monoethyl) ether;N-methyl-2-pyrrolidone; 1,3-dimethyl-2-imidazolidinone; triethanolamine;sulfolane; dimethyl sulfoxide; cyclic amide compounds such as2-pyrrolidone and ε-caprolactam; and imide compounds such assuccinimide.

In the inks according to this embodiment, a compound having a solubilityparameter value between the solubility parameter values of the twoorganic compounds incompatible with each other is preferably used incombination with these two organic compounds. As such a compound, isparticularly preferably used a glycol compound which is liquid at normaltemperature. When these compounds are used in combination in the ink,the stability in a state of an ink is improved without impairing theeffects of the present invention.

As a further preferred mode of the inks according to this embodiment, acompound having a vapor pressure not higher than that of triethyleneglycol is also used in combination. When such a compound is used incombination, the gas-liquid interface in a state of an ink become easyto be stably retained.

Although the preferred modes of this embodiment have been describedabove, a compound having a solubility parameter value smaller than 12and soluble in water is preferably used as a compound used incombination in view of generality. No particular limitation is imposedon the amount used. However, it is generally within a range ofpreferably from 0.1 to 15% by weight, more preferably from 0.1 to 10% byweight based on the total weight of the ink.

The content of such a water-soluble organic solvent as described aboveis generally within a range of preferably from 1 to 40% by weight, morepreferably from 3 to 30% by weight based on the total weight of the ink.The content of water in the ink is generally within a range of from 30to 95% by weight based on the total weight of the ink. If the content islower than 30% by weight, the solubility of the coloring material andthe like becomes deteriorated, and the viscosity of the resulting ink isalso increased. It is hence not preferable to use water in such a lowproportion. If the content of water exceeds 95% by weight on the otherhand, an evaporating component is too great to satisfy sufficientcrusting property.

In the inks according to this embodiment, a coloring material exhibitingno fluorescence properties may be contained to adjust the color tone ofthe inks. As the coloring material used in this case, a coloringmaterial soluble in water is preferred from the viewpoint of stabilityof the resulting ink (as with the fluorescent coloring material,including those seeming to be dissolved in water by, for example,emulsification in this case). When the water fastness of a recordedarticle formed by the ink according to the present invention is takeninto consideration, a coloring material (direct dye) directly coloring arecording medium is preferably used in view of the stability of theresulting ink as well. A coloring material having an azo group in itsstructure is more preferred. As the coloring material exhibiting nofluorescence properties, is preferably used a coloring material having acarboxyl group or its salt group in the structure thereof. A coloringmaterial having only a carboxyl group or its salt group as a hydrophilicgroup of the coloring material is more preferred for use. Since thecarboxyl group is weak in affinity for water compared with a sulfonicgroup, the water fastness of the recorded article formed by the inkaccording to the present invention can be improved.

The content of the coloring material exhibiting no fluorescenceproperties in the inks according to this embodiment is preferably notlower than the content of the coloring material exhibiting fluorescenceproperties as described above. When an ink is made up in such a manner,a recorded state tends to remain even when the coloring materialexhibiting fluorescence properties is lacking of water resistance, andfluorescence is lost by contact of the recorded article with water, sothat it is prevented to completely lose the details recorded. However,when the coloring material exhibiting no fluorescence properties isselected, it is preferable that it be suitably selected according to thedeveloped state of fluorescence properties in a recorded article formedby the compound exhibiting fluorescence properties and/or the coloringmaterial exhibiting fluorescence properties, or balance with thecoloring ability thereof.

Specific examples of the coloring material exhibiting no fluorescenceproperties include Direct Black 168, Direct Black 154, Direct Yellow145, Direct Yellow 86, Direct Red 227, Direct Blue 199 and coloringmaterials represented by the following general formulae (A) to (C) inthe form of a free acid. However, the present invention is not limitedto these coloring materials.

Coloring material represented by the general formula (A) in the form ofa free acid:Pc(SO₃H)_(t)(SO₂—NR¹-L-NR²—X—NR³-G)_(q)  (A)wherein Pc is a metallized phthalocyanine nucleus, R¹, R² and R³ are,independently of one another, H, alkyl group (for example, a linear orbranched alkyl group having 1 to 20 carbon atoms), substituted alkylgroup (for example, an alkyl group at least one hydrogen of which hasbeen substituted by halogen (fluorine, chlorine, bromine or the like),an alkoxy group having 1 to 3 carbon atoms, or the like), alkenyl group(for example, an alkenyl group having 1 to 20 carbon atoms), substitutedalkenyl group (for example, an alkenyl group at least one hydrogen ofwhich has been substituted by halogen (fluorine, chlorine, bromine orthe like), an alkoxy group having 1 to 3 carbon atoms, or the like),aralkyl group (for example, a phenylmethyl or phenylethyl group), orsubstituted aralkyl group (for example, an aralkyl group the aryl groupof which has been substituted by at least one substituent selected fromhalogen (fluorine, chlorine, bromine and the like), linear or branchedalkyl groups having 1 to 3 carbon atoms, alkoxy groups having 1 to 3carbon atoms, and the like), L is a divalent organic linking group (forexample, a methylene or ethylene group), X is a carbonyl group or agroup represented by the following formula (2), (3) or (4)

wherein Z in each of the formulae (2) to (4) is NR⁴R⁵, SR⁶ or OR⁶, Y inthe formula (3) is H, Cl, Z, SR⁷ or OR⁷, E in the formula (4) is Cl orCN, R⁴, R⁵, R⁶ and R⁷ are, independently of one another, H, alkyl group(for example, a linear or branched alkyl group having 1 to 20 carbonatoms), substituted alkyl group (for example, an alkyl group at leastone hydrogen of which has been substituted by halogen (fluorine,chlorine, bromine or the like), an alkoxy group having 1 to 3 carbonatoms, or the like), aryl group (for example, a phenyl group),substituted aryl group (for example, a phenyl group substituted by atleast one substituent selected from halogen (fluorine, chlorine, bromineand the like), alkoxy groups having 1 to 3 carbon atoms, linear orbranched alkyl groups having 1 to 3 carbon atoms, and the like), aralkylgroup (for example, a phenylmethyl or phenylethyl group), or substitutedaralkyl group (for example, an aralkyl group the aryl group of which hasbeen substituted by at least one substituent selected from halogen(fluorine, chlorine, bromine and the like), linear or branched alkylgroups having 1 to 3 carbon atoms, alkoxy groups having 1 to 3 carbonatoms, and the like), or R⁴ and R⁵ may be form a 5- or 6-membered ringtogether with nitrogen, G is a colorless organic residue substituted by1 or 2 COSHs or COOHs, and t+q is 3 or 4.

Examples of the compounds represented by the general formula (A) includeC.I. Direct Blue 307, and Exemplified Coloring Material (1):

Coloring material represented by the general formula (B) in the form ofa free acid:Ar¹N═NJX(NR¹LNR²X)_(n)JN═NAr²  (B)wherein J is the following formula

Ar¹ and Ar² are, independently of each other, an aryl group orsubstituted aryl group, at least one of Ar¹ and Ar² is a substitutedaryl group having at least one substituent selected from COOH and COSH,R¹ and R² are, independently of each other, H, alkyl group (for example,a linear or branched alkyl group having 1 to 20 carbon atoms),substituted alkyl group (for example, an alkyl group at least onehydrogen of which has been substituted by halogen (fluorine, chlorine,bromine or the like), an alkoxy group having 1 to 3 carbon atoms, or thelike), alkenyl group (for example, an alkenyl group having 1 to 20carbon atoms), or substituted alkenyl group (for example, an alkenylgroup at least one hydrogen of which has been substituted by halogen(fluorine, chlorine, bromine or the like), an alkoxy group having 1 to 3carbon atoms, or the like), L is a divalent organic linking group (forexample, —NH-φ-NH—, in which φ is a phenylene group), n is 0 or 1, and Xis a carbonyl group or a group represented by the following formula (2),(3) or (4)

wherein Z in each of the formulae (2) to (4) is NR³R⁴, SR⁵ or OR⁵, Y inthe formula (3) is H, Cl, Z, SR⁶ or OR⁶, E in the formula (4) is Cl orCN, R⁴, R⁵, R⁶ and R⁷ are, independently of one another, H, alkyl group(for example, a linear or branched alkyl group having 1 to 20 carbonatoms), substituted alkyl group (for example, an alkyl group at leastone hydrogen of which has been substituted by halogen (fluorine,chlorine, bromine or the like), an alkoxy group having 1 to 3 carbonatoms, or the like), alkenyl group (for example, an alkenyl group having1 to 20 carbon atoms), substituted alkenyl group (for example, analkenyl group at least one hydrogen of which has been substituted byhalogen (fluorine, chlorine, bromine or the like), an alkoxy grouphaving 1 to 3 carbon atoms, or the like), aryl group (for example, aphenyl group), substituted aryl group (for example, a phenyl groupsubstituted by at least one substituent selected from halogen (fluorine,chlorine, bromine and the like), alkoxy groups having 1 to 3 carbonatoms, linear or branched alkyl groups having 1 to 3 carbon atoms, andthe like), aralkyl group (for example, a phenylmethyl or phenylethylgroup), or substituted aralkyl group (for example, an aralkyl group thearyl group of which has been substituted by at least one substituentselected from halogen (fluorine, chlorine, bromine and the like), linearor branched alkyl groups having 1 to 3 carbon atoms, alkoxy groupshaving 1 to 3 carbon atoms, and the like), or R⁴ and R⁵ may be form a 5-or 6-membered ring together with nitrogen, with the proviso that thecompounds represented by the general formula (B) have at least the samenumber of groups selected from COOH and COSH as SO₃H.

Examples of the compounds represented by the general formula (B)includes C.I. Direct Violet 107 and

Coloring material represented by the general formula (C) in the form ofa free acid:

wherein Ar and Ar¹ are, independently of each other, an aryl group (forexample, a phenyl group) or substituted aryl group, at least one of Arand Ar¹ is a substituted aryl group having a substituent selected fromthe group consisting of sulfonic, carboxyl and thiocarboxyl groups, Jand J¹ are, independently of each other, a group represented by thefollowing formula (2), (3) or (4)

wherein R⁵ in the formula (2) is selected from hydrogen, alkyl groups(for example, linear or branched alkyl groups having 1 to 20 carbonatoms), substituted alkyl groups (for example, alkyl groups at least onehydrogen of which has been substituted by halogen (fluorine, chlorine,bromine or the like), an alkoxy group having 1 to 3 carbon atoms, or thelike), alkoxy groups (for example, methoxy and ethoxy groups), halogen(for example, fluorine, chlorine and bromine), CN, ureide group andNHCOR⁶ (R⁶ being selected from hydrogen, alkyl groups (for example,linear or branched alkyl groups having 1 to 20 carbon atoms),substituted alkyl groups (for example, alkyl groups at least onehydrogen of which has been substituted by halogen (fluorine, chlorine,bromine or the like), an alkoxy group having 1 to 3 carbon atoms, or thelike), aryl groups (for example, a phenyl group), substituted arylgroups (for example, a phenyl group substituted by at least onesubstituent selected from halogen (fluorine, chlorine, bromine and thelike), alkoxy groups having 1 to 3 carbon atoms, linear or branchedalkyl groups having 1 to 3 carbon atoms, and the like), aralkyl groups(for example, phenylmethyl and phenylethyl groups), and substitutedaralkyl group (for example, aralkyl groups the aryl group of which hasbeen substituted by at least one substituent selected from halogen(fluorine, chlorine, bromine and the like), linear or branched alkylgroups having 1 to 3 carbon atoms, alkoxy groups having 1 to 3 carbonatoms, and the like)), T in the formula (3) is an alkyl group, W isselected from hydrogen, CN CONR¹⁰R¹¹, pyridinium group and carboxylgroup, (R¹⁰ and R₁₁ being, independently of each other, selected fromhydrogen, alkyl groups (for example, linear or branched alkyl groupshaving 1 to 20 carbon atoms) and substituted alkyl groups (for example,alkyl groups at least one hydrogen of which has been substituted byhalogen (fluorine, chlorine, bromine or the like), an alkoxy grouphaving 1 to 3 carbon atoms, or the like)), m is an alkylene group having2 to 3 carbon atoms, B in the formula (4) is selected from hydrogen,alkyl groups and carboxy group, R⁴, R⁵, R⁶ and R⁷ in the formula (C)are, independently of one another, selected from H, alkyl groups (forexample, linear or branched alkyl groups having 1 to 20 carbon atoms)and substituted alkyl groups (for example, alkyl groups at least onehydrogen of which has been substituted by halogen (fluorine, chlorine,bromine or the like), an alkoxy group having 1 to 3 carbon atoms, or thelike), L is a divalent organic linking group (for example, —NH-φ-NH—, inwhich φ is a phenylene group), n is 0 or 1, and X is a carbonyl group ora group represented by the following formula (5), (6) or (7)

wherein Z in each of the formulae (5) to (7) is selected from OR⁷, SR⁷and NR⁸R⁹, Y is selected from hydrogen, Cl and Z, E is selected from Cland CN, R⁷, R⁸ and R⁹ are, independently of one another, hydrogen,alkenyl group (for example, an alkenyl group having 1 to 20 carbonatoms), substituted alkenyl group (for example, an alkenyl group atleast one hydrogen of which has been substituted by halogen (fluorine,chlorine, bromine or the like), an alkoxy group having 1 to 3 carbonatoms, or the like), alkyl group (for example, a linear or branchedalkyl group having 1 to 20 carbon atoms), substituted alkyl group (forexample, an alkyl group at least one hydrogen of which has beensubstituted by halogen (fluorine, chlorine, bromine or the like), analkoxy group having 1 to 3 carbon atoms, or the like), aryl group (forexample, a phenyl group), substituted aryl group (for example, a phenylgroup substituted by at least one substituent selected from halogen(fluorine, chlorine, bromine and the like), alkoxy groups having 1 to 3carbon atoms, linear or branched alkyl groups having 1 to 3 carbonatoms, and the like), aralkyl group (for example, a phenylmethyl orphenylethyl group), or substituted aralkyl group (for example, anaralkyl group the aryl group of which has been substituted by at leastone substituent selected from halogen (fluorine, chlorine, bromine andthe like), linear or branched alkyl groups having 1 to 3 carbon atoms,alkoxy groups having 1 to 3 carbon atoms, and the like), or R⁸ and R⁹may be form a 5- or 6-membered ring together with nitrogen, with theproviso that when the compounds of the general formula (C) have nosulfonic group, the compounds have at least 2 groups selected fromcarboxyl and thiocarboxyl groups, or the compounds of the generalformula (C) have at least the same number of groups selected fromcarboxyl and thiocarboxyl groups as the sulfonic group.

Examples of the compounds represented by the general formula (C)includes

No particular limitation is imposed on the amount of such coloringmaterial exhibiting no fluorescence properties as described above to beused. However, it is generally within a range of preferably from 0.1 to15% by weight, more preferably from 0.1 to 10% by weight based on thetotal weight of the ink.

For example, the inks according to this embodiment preferably have asurface tension of at most 40 mN/m (dyn/cm) because in order to developthe above-described mechanism, it is preferred from the viewpoint ofdevelopment of the effect that for example, an ink droplet spreads afterrecording. Further, the pH of the inks according to this embodiment ispreferably at least 8 from the viewpoint of stability of the inks.

In the inks according to this embodiment, it is preferred that an alkalimetal ion and an ammonium ion be used in combination as counter ions tothese coloring materials.

When both ions are used in combination, the stability and ejectionstability of the resulting ink are improved when the ink is used inink-jet recording. As examples of the alkali metal ion, may be mentionedLi⁺, Na⁺ and K⁺. The inks according to this embodiment are preferablyadjusted to nonionicity in an ink system from which the coloringmaterial and additives have been removed.

In the inks according to this embodiment, it is fluorescence intensityof the resulting image that the compound exhibiting fluorescenceproperties and/or the coloring material exhibiting fluorescenceproperties be contained in at least a concentration sufficient toexhibit the maximum fluorescence intensity in the inks. Inferentially,the reason for it is considered to be due to the fact that since theapparent concentration of a coloring material is lowered by featheringor bleeding, penetration and the like of an ink when recording isconducted with a water-based ink on a recording medium, good coloring isretained on a selected recording medium when recording is conducted onthe recording medium with the ink made up in such a manner.

The fluorescent inks according to this embodiment made up in theabove-described manner may also be used as inks for general writingutensils, but are particularly effective when used in ink-jet recording.Ink-jet recording methods include a recording method in which mechanicalenergy is applied to an ink to eject droplets of the ink, and arecording method in which thermal energy is applied to an ink to ejectdroplets of the ink by bubbling of the ink. The inks according to thisembodiment are particularly suitable for use in an ink-jet recordingmethod of a type that an ink is ejected by the bubbling phenomenon ofthe ink caused by thermal energy. This recording method has a featurethat the ejection of the ink becomes extremely stable, and no satellitedots generate. In this case, however, the thermal properties (forexample, specific heat, coefficient of thermal expansion, heatconductivity, etc.) of the inks may be controlled in some cases.

From the viewpoint of making the matching of the inks with an ink-jethead good, the inks according to this embodiment may desirably becontrolled so as to have, as their own physical properties at 25° C., asurface tension of 30 to 40 mN/m (dyn/cm) and a viscosity of 15 cP orlower, preferably 10 cP or lower, more preferably 5 cP or lower. Inorder to control the inks to the above physical property values to solveproblems in plain paper, the amount of water contained in the inksaccording to this embodiment is preferably controlled to not less than50% by weight, but not more than 98% by weight, more preferably not lessthan 60% by weight, but not more than 95% by weight.

Second Embodiment

The ink according to the second embodiment of the present invention willnow be described.

The ink according to the second embodiment has a feature that a glycolcompound having a vapor pressure higher than that of diethyleneglycol isadditionally contained in the above-described ink according to the firstembodiment. According to the ink according to this embodiment, in whichsuch a compound is used in combination, the coloring ability includingfluorescence intensity is made good, and so the fluorescence propertiesand coloring ability of the resulting recorded article are markedlyimproved, and moreover a separate excellent effect that the drawback ofthe conventional recorded articles exhibiting the fluorescenceproperties that the fluorescence intensity of a fluorescent coloringmaterial exposed to light is lowered with time can be effectivelyprevented is achieved.

With respect to the glycol compound having a vapor pressure higher thanthat of diethyleneglycol, which makes a difference from the inkaccording to the first embodiment, this compound is preferably acompound which dissolves or disperses the 2 organic compoundsincompatible with each other therein, and for example, its solubilityparameter value is preferably between the solubility parameter values ofthe 2 organic compounds incompatible with each other. When such acompound is used in combination, the drawback of the conventionalrecorded articles exhibiting the fluorescence properties that thefluorescence intensity of the fluorescent coloring material exposed tolight is lowered with time can be effectively prevented as describedabove. Specific examples of such a compound vary according to the twoorganic compounds used. When for example, the above-described organiccompound having a glycerol group and nonionic surfactant are used as thetwo organic compounds, however, it is preferable to use a glycolcompound. Examples of such a compound include glycol compounds having avapor pressure not lower than that of ethylene glycol, specifically,ethylene glycol (Vapor pressure: 6.7 Pa at 20° C.) and diethylene glycol(vapor pressure: <1.3 Pa at 20° C.).

With respect to the reason why the ink according to this embodimentexhibits such effects as described above, the present inventors areconsidered to be attributable to evaporation of the compound having avapor pressure not lower than that of diethyleneglycol, for example,ethyleneglycol or diethylene glycol on a recording medium. Morespecifically, since the evaporation of such a compound is comparativelymild, said compound is contained in plenty in the ink just after an inkdroplet is applied to the recording medium. Therefore, it is consideredthat said compound is present at the liquid-liquid interface 1107between the layers 1101 and 1103 in FIG. 11, or at least one of theliquid-liquid interfaces 1107 between the layers 1201 and 1203 andbetween the layers 1203 and 1205 in FIG. 12 to inhibit the formation ofa clear interface. Namely, a recorded portion by the ink according tothis embodiment exhibits weaker fluorescence intensity that thatexhibited by a recorded portion obtained by an ink not containing saidink just after recording. However, said compound gradually evaporateswith time. As a result, the liquid-liquid interface is made clear,resulting in formation of a recorded portion suitable for obtaining highfluorescence intensity. The fluorescence-emitting ability of thecompound exhibiting fluorescence properties or the coloring materialexhibiting fluorescence properties may be lowered with time in somecases according to an environment in which the recording article isplaced. However, the apparent fluorescence intensity of the recordedportion formed by the ink according to this embodiment is extremelyeffectively prevented from being deteriorated with time or scarcelydeteriorated or may be increased in some cases. Accordingly, when arecorded article is expected to have longer fluorescence properties, itis preferable to use the ink according to this embodiment.

As a preferred method and an apparatus for conducting recording by usingthe inks according to the present invention, may be mentioned a methodand an apparatus in which thermal energy corresponding to recordingsignals is applied to an ink within a recording head, and ink dropletsare generated by the thermal energy.

Examples of the construction of a head, which is a main component ofsuch an apparatus, are illustrated in FIGS. 1, 2 and 3. FIG. 1 is across-sectional view of a head 13 taken along the flow path of ink, andFIG. 2 is a cross-sectional view taken along line 2—2 in FIG. 1. Thehead 13 is formed by bonding a glass, ceramic, silicon or plastic plateor the like having a groove 14 through which an ink is passed, to aheating head 15 which is used for thermal recording (the drawings show athin-film head to which, however, the invention is not limited). Theheating head 15 is composed of a protective film 16 made of siliconoxide or the like, aluminum electrodes 17-1 and 17-2, a heating resistorlayer 18 made of nichrome or the like, a heat accumulating layer 19, anda substrate 20 made of alumina or the like having a good heat radiatingproperty.

An ink 21 comes up to an ejection orifice (a minute opening) 22 andforms a meniscus 23 due to a pressure P. Now, upon application ofelectric signals to the aluminum electrodes 17-1 and 17-2, the heatinghead 15 rapidly generates heat at the region shown by “n” to formbubbles in the ink 21 which is in contact with this region. The meniscus23 of the ink is projected by the pressure thus produced, and the ink 21is ejected in the form of ink droplets 24 from the ejection orifice 22toward a recording medium 25.

FIG. 3 illustrates an appearance of a multi-head composed of an array ofa number of heads as shown in FIG. 1. The multi-head is formed byclosely bonding a glass plate 27 having a number of grooves 26 to aheating head 28 similar to that described in FIG. 1.

FIG. 4 illustrates an example of an ink-jet recording apparatus in whichsuch a head as described above has been incorporated. In FIG. 4,reference numeral 61 designates a blade serving as a wiping member, oneend of which is a stationary end held by a blade-holding member to forma cantilever. The blade 61 is provided at a position adjacent to aregion in which a recording head 65 operates, and in this embodiment, isheld in such a form that it protrudes into the course through which therecording head 65 is moved. Reference numeral 62 indicates a cap for theface of ejection openings of the recording head 65, which is provided ata home position adjacent to the blade 61, and is so constructed that itmoves in a direction perpendicular to a direction in which the recordinghead 65 is moved, and comes into contact with the face of ejectionopenings to cap it. Reference numeral 63 denotes an ink absorbing memberprovided adjoiningly to the blade 61 and, similar to the blade 61, heldin such a form that it protrudes into the course through which therecording head 65 is moved.

The above-described blade 61, cap 62 and ink absorbing member 63constitute an ejection-recovery portion 64, where the blade 61 and inkabsorbing member 63 remove water, dust and/or the like from the face ofthe ink-ejecting openings. Reference numeral 65 designates the recordinghead having an ejection-energy-generating means and serving to eject theink onto a recording medium set in an opposing relation to the ejectionopening face provided with the ejection openings to conduct recording.Reference numeral 66 indicates a carriage on which the recording head 65is mounted so that the recording head 65 can be moved. The carriage 66is slidably interlocked with a guide shaft 67 and is connected (notillustrated) at its part to a belt 69 driven by a motor 68. Thus, thecarriage 66 can be moved along the guide shaft 67 and hence, therecording head 65 can be moved from a recording region to a regionadjacent thereto.

Reference numerals 51 and 52 denote a feeding part from which therecording medium is inserted, and feed rollers driven by a motor (notillustrated), respectively. With such a construction, the recordingmedium is fed to the position opposite to the ejection opening face ofthe recording head 65, and discharged from a discharge section providedwith discharge rollers 53 with the progress of recording.

In the above construction, the cap 62 in the ejection-recovery portion64 is receded from the path of motion of the recording head 65 when therecording head 65 is returned to its home position after completion ofrecording, and the blade 61 remains protruded into the path of motion.As a result, the ejection opening face of the recording head 65 iswiped. When the cap 62 comes into contact with the ejection opening faceof the recording head 65 to cap it, the cap 62 is moved so as toprotrude into the path of motion of the recording head 65.

When the recording head 65 is moved from its home position to theposition at which recording is started, the cap 62 and the blade 61 areat the same positions as the positions for the wiping as describedabove. As a result, the ejection opening face of the recording head 65is also wiped at the time of this movement. The above movement of therecording head 65 to its home position is made not only when therecording is completed or the recording head 65 is recovered forejection, but also when the recording head 65 is moved between recordingregions for the purpose of recording, during which it is moved to thehome position adjacent to each recording region at given intervals,where the ejection opening face is wiped in accordance with thismovement.

FIG. 5 illustrates an exemplary ink cartridge 45 in which an ink to befed to a head through a member for feeding the ink, for example, a tubeis contained. Here, reference numeral 40 designates an ink containercontaining the ink to be fed, as exemplified by a bag for ink. One endthereof is provided with a stopper 42 made of rubber. A needle (notillustrated) may be inserted into this stopper 42 so that the ink in thebag 40 for ink can be fed to the head. Reference numeral 44 indicates anink absorbing member for receiving a waste ink. It is preferred that theink container 40 be formed of a polyolefin, in particular, polyethylene,at its surface with which the ink comes into contact.

The ink-jet recording apparatus according to the present invention arenot limited to the apparatus as described above in which the head andthe ink cartridge are separately provided. Therefore, a device in whichthese members are integrally formed as shown in FIG. 6 can also bepreferably used. In FIG. 6, reference numeral 70 designates a recordingunit, in the interior of which an ink container containing an ink, forexample, an ink holding member, is contained. The recording unit 70 isso constructed that the ink in such an ink holding member is ejected inthe form of ink droplets through a head portion 71 having a plurality oforifices.

In the present invention, polyurethane, cellulose, polyvinyl acetate,polyolefin or a polymer formed by a condensation or polymerizationreaction of organic compound(s) is preferably used as a material for theink holding member. Further, an ink holding member composed of a porousmaterial or having a multi-layer structure is preferably used. It ispreferred that an ink holding member the direction of the multi-layerarrangement of the multi-layer structure of which is aligned in an inkdischarging direction of the ink container be used. It is also preferredthat an ink holding member having a contact surface with the inkcontainer be used. Reference numeral 72 indicates an air passage forcommunicating the interior of the recording unit 70 with the atmosphere.This recording unit 70 is used in place of the recording head 65 shownin FIG. 4, and is detachably installed on the carriage 66.

Other specific examples of the recording apparatus and recording headspreferably used in the present invention will hereinafter be described.FIG. 13 is a schematic perspective view illustrating principal parts ofa liquid-ejecting head of an ejection system that a bubble communicateswith the atmosphere upon ejection, and an exemplary ink-jet printer as aliquid-ejecting apparatus using this head.

In FIG. 13, the ink-jet printer comprises a cunveying device 1030 forintermittently conveying paper 1028 as a recording medium provided alongthe longitudinal direction in a casing 1008 in a direction shown by anarrow P in FIG. 13, a recording part 1010 reciprocatingly moved in adirection substantially parallel to a guide shaft 1014 in a direction ofan arrow S substantially perpendicular to the conveying direction P ofthe paper 1028 by the conveying device 1030, and a driving part 1006 formovement as a driving means for reciprocatingly moving the recordingpart 1010.

The conveying device 1030 comprises a pair of roller units 1022 a and1022 b and a pair of roller units 1024 a and 1024 b arranged insubstantial parallel with and in opposed relation to each other, and adriving part 1020 for driving these respective roller units. By thisconstruction, the paper 1028 is intermittently conveyed in a state thatit is held between the respective roller units 1022 a and 1022 b and theroller units 1024 a and 1024 b in a direction shown by the arrow P inFIG. 13 when the driving part 1020 of the conveying device 1030 isoperated.

The driving part 1006 for movement comprises a belt 1016 wound aroundpulleys 1026 a and 1026 b respectively provided on rotating shaftsoppositely arranged at a prescribed interval and a motor 1018 fordriving the belt 1016 joined to a carriage member 1010 a of therecording part 1010 arranged in substantial parallel to the roller units1022 a and 1022 b in forward and reverse directions.

When the motor 1018 is operated to rotate the belt 1016 in a directionshown by an arrow R in FIG. 13, the carriage member 1010 a of therecording part 1010 is moved by the prescribed movement in the directionshown by the arrow S in FIG. 13. When the motor 1018 is operated torotate the belt 1016 in a direction reverse to the direction shown bythe arrow R in FIG. 13, the carriage member 1010 a of the recording part1010 is moved by the prescribed movement in a direction reverse to thedirection shown by the arrow S in FIG. 13. At an end of the driving part1006 for movement, a recovery unit 1026 for conducting anejection-recovery operation for the recording part 1010 is provided inopposed relation to an array of ink-ejection openings of the recordingpart 1010 at the home position of the carriage member 1010 a.

In the recording part 1016, ink-jet cartridges (hereinafter may bereferred merely to as “cartridges” in some cases) 1012Y, 1012M, 1012Cand 1012B for respective colors, for example, yellow, magenta, cyan andblack, are detachably mounted on a carriage member 1010 a.

FIG. 14 illustrates an exemplary ink-jet cartridge capable of beingmounted on the above-described ink-jet recording apparatus. Thecartridge 1012 in this embodiment is of a serial type, and its principalpart is constructed by an ink-jet recording head 100 and a liquid tank1001 for containing a liquid such as an ink.

In the ink-jet recording head 100, a great number of ejection openings832 for ejecting the liquid are formed, and the liquid such as an ink isdirected to a common liquid chamber (see FIG. 15) in the liquid-ejectinghead 100 through a liquid feed passage (not illustrated) from the liquidtank 1001. The cartridge 1012 shown in FIG. 14 is so constructed thatthe ink-jet recording head 100 and the liquid tank 1001 are integrallyformed, and the liquid can be supplied to the interior of the liquidtank 1001 as needed. However, a structure that the liquid tank 1001 isreplaceably joined to this liquid-ejecting head 100 may also be adopted.

A specific example of the above-described liquid-ejecting head capableof being mounted on the ink-jet printer of such a construction willhereinafter be described in detail.

FIG. 15 is a schematic perspective view typically illustrating principalparts of a liquid-ejecting head suitable for use in the ink-jetrecording apparatus of the present invention, and FIGS. 16 to 19 arefront views illustrating the form of ejection openings of theliquid-ejecting head shown in FIG. 14. Incidentally, in these drawings,electrical wiring and the like for driving electrothermal conversionelements are omitted.

In the liquid-ejecting head according to this embodiment, such asubstrate 934 composed of glass, ceramic, plastic or metal asillustrated in, for example, FIG. 15 is used. The material of such asubstrate is not essential to the present invention and is notparticularly limited so far as it functions as a part of a flow-pathforming member and as a support for an ink ejection-energy-generatingelement, and a material layer for forming a liquid flow path andejection openings, which will be described subsequently. Therefore, inthis embodiment, the description is given in the case where an Sisubstrate (wafer) is used. The ejection openings can be formed on such asubstrate 934. Processes therefor include a forming process by laserbeam, and a process in which for example, a photosensitive resin is usedas an orifice plate (ejection-opening plate) 935, which will bedescribed subsequently, to form ejection openings by an aligner such asMPA (mirror projection aligner).

In FIG. 15, reference numeral 934 indicates a substrate equipped withelectrothermal conversion elements (hereinafter may be referred as“heater” in some cases) 931 and an ink feed opening 933 formed of along-grooved through-opening as a common liquid chamber. The heaters931, which are thermal energy-generating means, are arranged in a zigzagform in a row on both sides of the ink feed opening 933 along thelongitudinal direction thereof with an interval of, for example, 300 dpibetween the electrothermal conversion elements. Walls 936 for ink flowpath for forming ink flow paths are provided on the substrate 934.Further, an ejection-opening plate 935 equipped with ejection openings832 is provided on the walls 936 for ink flow path.

In FIG. 15, the walls 936 for ink flow path and the ejection-openingplate 935 are illustrated as separate members. However, the walls 936for ink flow path may be formed on the substrate 934 by a method such asspin coating, thereby forming the walls 936 for ink flow path and theejection-opening plate 935 as the same member at the same time. In thisembodiment, the side of the ejection-opening face (upper surface) 935 ais subjected to a water-repellent treatment.

In the apparatus illustrated, a head of the serial type that recordingis conducted while scanning in the direction shown by the arrow S inFIG. 13 is used to conduct recording at, for example, 1,200 dpi. Drivingfrequency is 10 kHz, and ejection is conducted at the shortest timeinterval of 100 μs in one ejection opening.

As an example of dimensions of the head, a partition wall 936 a forisolating adjacent nozzles from each other from the viewpoint of fluidhas a width w of 14 μm as illustrated in, for example, FIG. 16. Asillustrated in FIG. 19, a bubbling chamber 1337 formed by the walls 936for ink flow path has N₁ (width of the bubbling chamber) of 33 μm and N₂(length of the bubbling chamber) of 35 μm. The size of the heater 931 is30 μm×30 μm, the resistance value of the heater is 53 Ω, and drivingvoltage is 10.3 V. A head in which the heights of the wall 936 for inkflow path and the partition wall 936 a are 12 μm, and the thickness ofthe ejection-opening plate is 11 μm may be used.

In the section of an ejection opening part 940 provided in theejection-opening plate including ejection openings 832, the form of asection taken along a direction intersecting the ejecting direction(thickness-wise direction of the orifice plate 935) of the ink is asubstantially star form as illustrated in FIG. 17 and is generallyformed by 6 projected portions 832 a having a corner of an obtuse angleand 6 recessed portions 832 b alternately arranged between theseprojected portions 832 a and having a corner of an acute angle. Morespecifically, 6 grooves (with respect to the position of the grooveportion, see 1141 a in FIG. 20) are formed in the thickness-wisedirection (ejecting direction of the liquid) of the orifice plate shownin FIG. 15 by using the recessed portion 832 b locally distant from thecenter O of the ejection opening as a top thereof and the projectedportion 832 a adjacent to this region and locally near from the center Oof the ejection opening as a base.

In the liquid-ejecting head illustrated, the ejection opening part 940is such that, for example, a section taken along a directionintersecting the thickness-wise direction thereof is in a form with 2equilateral triangle having a side of 27 μm combined with each other ina state that one of them has been turned by 60 degrees. T₁ shown in FIG.17 is 8 μm. The angles of the projected portions 832 a are all 120degrees, while the angles of the recessed portions 832 b are all 60degrees.

Accordingly, the center O of the ejection opening consists with thecenter of gravity G of a polygon formed by connecting centers (center(center of gravity) of a figure formed by connecting the top of thegroove and 2 bases adjacent to the top) of the grooves adjacent to eachother (see FIG. 17). The opening area of the ejection opening 832 inthis embodiment is 400 μm², and the opening area (area of the figureformed by connecting the top of the groove and 2 bases adjacent to thetop) of the groove is about 33 μm² per groove.

FIG. 18 is a typical drawing illustrating a state that an ink hasattached to the ejection opening portion shown in FIG. 17. In FIG. 18,reference character C indicates a part to which the ink has beenattached.

An ejecting operation of a liquid by the ink-jet recording head of theabove-described construction will hereinafter be described withreference to FIGS. 20 to 27.

FIGS. 20 to 27 are cross-sectional views for illustrating the ejectingoperation of a liquid by the liquid-ejecting head shown in FIGS. 15 to19 and are cross-sectional views of the bubbling chamber 1337 shown inFIG. 19 taken along line 20—20. In this section, an end of the ejectionopening part 940 in the thickness-wise direction of the orifice plate isthe top 1141 a of a groove 1141.

FIG. 20 illustrates a state that a film-like bubble has been formed onthe heater, and FIGS. 21, 22, 23, 24, 25, 26 and 27 illustrate statesafter about 1 μs from the state in FIG. 20, after about 2 μs from thestate in FIG. 20, after about 3 μs from the state in FIG. 20, afterabout 4 μs from the state in FIG. 20, after about 5 μs from the state inFIG. 20, after about 6 μs from the state in FIG. 20 and after about 7 μsfrom the state in FIG. 20, respectively. Incidentally, in the followingdescription, “drop” or “drop-in” does not mean drop in the so-calledgravity direction, but means the movement in the direction of anelectrothermal conversion element irrespective of the installingdirection of a head.

When a bubble 101 is first formed in a liquid flow path 1338 on a heater931 by energizing the heater 931 on the basis of a recording signal orthe like as illustrated in FIG. 20, the bubble quickly volumetricallyexpands and grows during about 2 μs as illustrated in FIGS. 21 and 22.The height of the bubble 101 in the greatest volume exceeds the face 935a of an ejection opening. At this time, the pressure of the bubbledecreases from one to several to one to several tens as high as theatmospheric pressure.

At the time about 2 μs have elapsed from the formation of the bubble,the volume of the bubble 101 turns from the greatest volume to decreasedvolume as described above, and at substantially the same time as this,the formation of a meniscus 1004 is started. The meniscus 1004 alsorecedes, i.e., drops in the direction of the heater 931 as illustratedin FIG. 23.

In this embodiment, the ejection opening part in the liquid-ejectinghead illustrated has a plurality of grooves 1141 in a dispersed state,whereby capillary force acts in an opposite direction F_(C) to thereceding direction F_(M) of the meniscus at the portion of the groove1141 when the meniscus 1004 recedes. As a result, the forms of themeniscus and a main droplet (hereinafter may be referred to as “liquid”or “ink” in some cases) I when the meniscus recedes are compensated soas to give substantially symmetrical forms to the center of the ejectionopening even if some variation is observed in the state of the bubble101 by some cause.

In the liquid-ejecting head illustrated, the dropping velocity of thismeniscus 1004 is faster than the contracting velocity of the bubble 101,so that the bubble 101 communicates with the atmosphere in the vicinityof the lower surface of the ejection opening 832 at the time about 4 μshave elapsed from the formation of the bubble as illustrated in FIG. 24.At this time, the liquid (ink) in the vicinity of the central axis ofthe ejection opening 832 drops toward the heater 931 because the liquid(ink) I pulled back on the side of the heater 931 by the negativepressure of the bubble 101 before the communication with the atmosphereretains the velocity in the direction toward the heater 931 by virtue ofinertia even after the communication with the atmosphere.

The liquid (ink) dropped toward the side of the heater 931 reaches thesurface of the heater 931 at the time about 5 μs have elapsed from theformation of the bubble as illustrated in FIG. 25, and spreads so as tocover the surface of the heater 931 as illustrated in FIG. 26. Theliquid spread so as to cover the surface of the heater 931 as describedabove has a vector in a horizontal direction along the surface of theheater 931. However, a vector in a direction intersecting the surface ofthe heater 931, for example, vertical direction vanishes, so that theliquid intends to remain on the surface of the heater 931, therebypulling a liquid located on the upper side than such a liquid, i.e., aliquid keeping a velocity vector in the ejecting direction, downward.

Thereafter, a liquid portion I_(b) between the liquid spread on thesurface of the heater 931 and the liquid (main droplet) located on theupper side becomes thin, and is broken in the center of the surface ofthe heater 931 at the time about 7 μs have elapsed from the formation ofthe bubble as illustrated in FIG. 27, whereby the liquid is separatedinto a main droplet I_(a) keeping a velocity vector in the ejectingdirection and a liquid I_(c) spread on the surface of the heater 931.The position of such separation is desirably the interior of the liquidflow path 1338, preferably a side closer to the electrothermalconversion element 931 than the ejection opening 832.

The main droplet I_(a) is ejected from the central portion of theejection opening 832 without deviation in the ejecting direction andejection slippage and impacted at the prescribed position of a recordingsurface on a recording medium. The liquid I_(c) spread on the surface ofthe heater 931 is ejected as a satellite droplet following the maindroplet up to now. However, it remains on the surface of the heater 931without being ejected.

Since the ejection of the satellite droplet can be prevented asdescribed above, splash easy to occur by the ejection of the satellitedroplet can be prevented, and staining of the recording surface on therecording medium with mist suspending in the form of fog can be surelyprevented. In FIGS. 24 to 27, reference characters I_(d) and I_(e)indicate an ink (ink within the groove) attached to the groove portionand an ink remaining in the liquid flow path, respectively.

As described above, in the liquid-ejecting head illustrated, thedirection of the main droplet upon ejection can be stabilized by theplural grooves dispersed to the center of the ejection opening when theliquid is ejected at the stage that the volume of the bubble decreasesafter growing into the greatest volume. As a result, a liquid-ejectinghead free of slippage in the ejecting direction and high in impactaccuracy can be provided. In addition, ejection can be stably conductedagainst the variation of bubbling at high driving frequency, wherebyhigh-speed and high-definition printing can be realized.

In particular, in the liquid-ejecting head illustrated, the liquid isejected by communicating the bubble with the atmosphere for the firsttime at the stage that the volume of the bubble decreases, whereby mistoccurred upon the ejection of the droplet by communicating the bubblewith the atmosphere can be prevented, so that the state that dropletsattach to the ejection opening face, which forms the main cause of theso-called sudden ejection failure, can also be inhibited.

As another embodiment of the recording head of the ejection system thata bubble is communicated with the atmosphere upon ejection, may bementioned the so-called edge shooter type as described in, for example,Japanese Patent Registration No. 2783647.

In particular, the present invention has excellent effects in recordingheads and recording apparatus of an ink-jet system that thermal energyis utilized to form a droplet to be ejected, thereby conductingrecording, among the ink-jet recording systems.

With respect to the typical construction and principle thereof, thoseusing the basic principle disclosed in, for example, U.S. Pat. Nos.4,723,129 and 4,740,796 are preferred.

This system may be applied to any of the so-called On-Demand type andcontinuous type. In particular, the On-Demand type is effective becauseat least one driving signal which corresponds to recording informationand gives a rapid temperature rise exceeding film boiling is applied toan electrothermal converter arranged corresponding to a sheet or liquidpath, in which a liquid (ink) is held, thereby causing theelectrothermal converter to generate thermal energy to cause filmboiling on the heat-acting surface of a recording head, so that a bubblecan be formed in the liquid (ink) in response to the driving signal inrelation of one to one. The liquid (ink) is ejected through an ejectionopening by the growth-contraction of this bubble to form at least onedroplet. When the driving signal is applied in the form of a pulse, thegrowth-contraction of the bubble is suitably conducted in a moment, sothat the ejection of the liquid (ink) excellent in responsiveness inparticular can be achieved. It is therefore preferable to use suchpulsed signals.

As the pulsed driving signal, such signals as described in U.S. Pat.Nos. 4,463,359 and 4,345,262 are suitable. When the conditions describedin U.S. Pat. No. 4,313,124 that is an invention relating to the rate oftemperature rise on the heat-acting surface are adopted, far excellentrecording can be conducted.

As the construction of the recording head which makes up the inkcartridge, recording unit and ink-jet recording apparatus according tothe present invention, such combined constructions (linear liquid flowpath or perpendicular liquid flow path) of ejection openings, a liquidflow path and electrothermal converters as disclosed in theabove-described U.S. specifications, and besides constructions based onU.S. Pat. Nos. 4,558,333 and 4,459,600 which disclose the constructionthat a heat-acting portion is arranged in a curved region may also bepreferably used.

In addition, constructions based on Japanese Patent ApplicationLaid-Open No. 59-123670 which discloses the construction that a slitcommon to a plurality of electrothermal converters are used as anejection part of the electrothermal converters, and Japanese PatentApplication Laid-Open No. 59-138461 which discloses the constructionthat an opening absorbing pressure wave of thermal energy is provided inopposition to an ejection part may also be effective for the presentinvention.

Further, as a full-line type recording head having a lengthcorresponding to the longest width of recording media, on which arecording apparatus can record, both construction that the length is metby such a combination of plural recording heads as disclosed in theabove-described specifications and construction as one recording headintegrally formed may be used, and the above-described effects of thepresent invention can be more effectively exhibited.

In addition, the present invention is effective even when a replaceable,chip type recording head in which electrical connection to an apparatusbody and the feed of an ink from the apparatus body become feasible byinstalling in the apparatus body, or a cartridge type recording head inwhich an ink tank is provided integrally in a recording head itself isused.

Further, the addition of recovery means for a recording head,preliminary auxiliary means, etc. which are provided as constitution ofthe recording apparatus according to the present invention is preferredbecause the effects of the present invention can be more stabilized.Specifically, capping means for the recording head, cleaning means,pressurizing or sucking means, preliminary heating means byelectrothermal converters, other heating elements than these orcombinations thereof, and preliminary ejection mode that ejectionseparate from recording is conducted may also be effective for stablerecording.

As a recording mode of the recording apparatus, the present invention isextremely effective for not only recording mode using main colors suchas black, but also apparatus equipped with at least one of complex colorof different colors and full color by color mixing by integrallyconstructing a recording head or combining plural recording heads witheach other.

In the above-described embodiments of the present invention, the inkshave been described as liquid. However, inks solidified at roomtemperature or lower may also be used so far as they are softened orliquid at room temperature, or exhibit a liquid phase upon applicationof recording signals used because it is general in the above-describedink-jet systems that the temperature control of an ink itself isconducted within a range of from 30 to 70° C. to adjust the viscosity ofthe ink so as to fall within a stable ejection range.

In addition, inks that are liquefied by applying thermal energyaccording to recording signals and ejected as liquid inks, such as inksthat temperature rise by thermal energy is positively prevented by usingthe thermal energy as energy for phase change from a solid phase to aliquid phase and inks solidified in a state left to stand for thepurpose of preventing evaporation of the inks, and inks of a nature thatthey are liquefied for the first time by thermal energy, such as thosealready beginning to solidify at the time they reach a recording medium,may also be applied to the present invention. In such a case, the inksmay be in a form that they are opposed to electrothermal converters in astate retained as a liquid or solid in recesses or through-holes in aporous sheet as described in Japanese Patent Application Laid-Open No.54-56847 or 60-71260. In the present invention, the above-described filmboiling system is most effective for the above-described inks.

Furthermore, as forms of the recording apparatus according to thepresent invention, forms that the apparatus is integrally or separatelyprovided as an image output terminal for information processinginstruments such as word processors and computers, and forms such ascopying machines combined with a reader and facsimiles having atransmitting-receiving function may also be adopted.

The outline of a liquid-ejecting apparatus in which the above-describedliquid-ejecting head is installed will hereinafter be described.

FIG. 28 is a schematic perspective view of an ink-jet recordingapparatus 600 which is an example of a liquid-ejecting apparatus towhich the liquid-ejecting head described above can be installed andapplied.

In FIG. 28, an ink-jet head cartridge 601 is so constructed that theabove-described liquid-ejecting head is integrally formed with an inktank with an ink to be fed to the liquid-ejecting head held therein. Theink-jet head cartridge 601 is mounted on a carriage 607 engaged with aspiral groove 606 in a leadscrew 605 rotating through drivingforce-transmitting gears 603 and 604 interlocking with the forward andreverse rotations of a driving motor 602 and reciprocatingly moved indirections shown by arrows a, b along a guide 608 together with thecarriage 607 by the power of the driving motor 602. A recording mediumP′ is conveyed on a platen roller 609 by a recording medium-conveyingmeans (not illustrated) and pressed against the platen roller 609 overthe moving direction of the carriage 607 by a paper presser plate 610.

Photocouplers 611 and 612 are arranged in the vicinity of an end of theleadscrew 605. These are home position-detecting means for confirmingthe presence of a lever 607 a of the carriage 607 in this region toconduct change-over of the rotating direction of the driving motor 602,and the like.

A support member 613 serves to support a cap member 614 covering thefront surface (ejection opening face) of the ink-jet head cartridge 601,in which ejection openings are present. An ink-sucking means 615 servesto suck an ink stored in the interior of the cap member 614 by emptyejection or the like from the ink-jet head cartridge 601. By thisink-sucking means 615, suction recovery of the ink-jet head cartridge601 is conducted through an opening (not illustrated) in the cap. Acleaning blade 617 for wiping the ejection opening face of the ink-jethead cartridge 601 is provided movably in forward and backwarddirections (directions perpendicular to the moving directions of thecarriage 607) by a moving member 618. These cleaning blade 617 andmoving member 618 are supported by a body support 619. The cleaningblade 617 is not limited to this form, and any other well-known cleaningblade may be used.

Upon the suction recovery operation of the liquid-ejecting head, a lever620 for initiating suction is moved with the movement of a cam 621engaged with the carriage 607, and the driving power from the drivingmotor 602 is transfer-controlled by a publicly known means such asclutch shift. An ink-jet recording control part for applying a signal toa heater provided in the liquid-ejecting head of the ink-jet headcartridge 601 and conducting drive control of the above-describedrespective mechanisms is provided on the side of the apparatus body andnot illustrated here.

The ink-jet recording apparatus 600 having the above-describedconstruction conducts recording on the recording medium P′ conveyed onthe platen roller 609 by the recording medium-conveying means (notillustrated) while reciprocatingly moving the ink-jet head cartridge 601over the full width of the recording medium P′.

Preferred modes of the inks according to the present invention describedabove, and preferred modes of the ink-jet recording process using theseinks, the recorded articles formed by the process, the recording unit,the ink-jet cartridge and the ink-jet recording apparatus willhereinafter be shown collectively.

The inks according to the first embodiment of the present invention havea feature that they comprise the 2 organic compounds incompatible witheach other, the compound exhibiting fluorescence properties and/or thecoloring material exhibiting fluorescence properties, and the liquidmedium dissolving or dispersing the 2 organic compounds incompatiblewith each other, the compound exhibiting fluorescence properties and/orthe coloring material exhibiting fluorescence properties therein. Theyare preferably water-based inks. In addition, they are preferably inkssuitable for use in ink-jet recording. Further, the content of thecompound exhibiting fluorescence properties and/or the coloring materialexhibiting fluorescence properties in the inks is preferably controlledto at most 1.5% by weight, more preferably at most 1.0% by weight. Thecompound exhibiting fluorescence properties and/or the coloring materialexhibiting fluorescence properties used is preferably water-soluble orhydrophilic. They are preferably inks that the content of thefluorescent coloring material in the inks is such that the content ofthe compound exhibiting fluorescence properties and/or the coloringmaterial exhibiting fluorescence properties in the inks is at least aconcentration sufficient to exhibit the maximum fluorescence intensityin the inks, and particularly the content of the compound exhibitingfluorescence properties and/or the coloring material exhibitingfluorescence properties in the inks is at least a concentrationsufficient to exhibit the maximum fluorescence intensity in the inks ina state dissolved in water.

As the 2 organic compounds incompatible with each other making up theinks according to the present invention, it is preferred that one of the2 organic compounds incompatible with each other has a solubilityparameter of at least 15, and the other has a solubility parameter of atmost 13, that the 2 organic compounds incompatible with each other areboth nonpolar compounds, that the 2 organic compounds incompatible witheach other are both water-soluble, that the 2 organic compoundsincompatible with each other are both liquid, that one of the 2 organiccompounds incompatible with each other has a glycerol group, and thatthe organic compound having a glycerol group is a compound having atleast 3 hydroxyl groups. The inks are preferably liquid at normaltemperature. Further, it is preferable to use a nonionic surfactant asthe other of the 2 organic compounds incompatible with each other. It isparticularly preferred that the nonionic surfactant is liquid at normaltemperature, or HLB of the nonionic surfactant is at most 13. It is alsopreferred that when the nonionic surfactant is contained in the inks,the nonionic surfactant is contained in the inks in an amount that thenonionic surfactant is not separated at an interface of an aqueoussolution in a state of the aqueous solution, and that the nonionicsurfactant is contained in the inks in an amount that the nonionicsurfactant is not separated at an interface of the ink in a state of anink from which the compound exhibiting fluorescence properties and/orthe coloring material exhibiting fluorescence properties has beenremoved.

Preferred modes of the inks according to the present invention includean ink that the nonionic surfactant making up the ink has an acetylenegroup, and an ink that the nonionic surfactant has a structurerepresented by the following general formula (I)

wherein A and B are, independently of each other, C_(n)H_(2n+1) (n beingan integer of 1 to 10), and X and Y are, independently of each other, aring-opening ethylene oxide unit and/or a ring-opening propylene oxideunit.

Further preferred modes of the inks according to the present inventioninclude an ink in which a monohydric alcohol is contained in addition tothe above-described basic components, and an ink in which a coloringmaterial exhibiting no fluorescence properties is additionallycontained. The coloring material exhibiting no fluorescence propertiesused in this case is preferably a coloring material having awater-solubility. Further, the coloring material exhibiting nofluorescence properties is preferably a coloring material directlycoloring a recording medium, more preferably an azo dye. As furtherpreferred modes of the inks, may be mentioned an ink in which thecontent of the coloring material exhibiting no fluorescence propertiesin the inks is higher than the content of the fluorescent coloringmaterial, an ink in which the coloring material exhibiting nofluorescence properties has a carboxyl group or its salt group, and anink in which at least one ammonium ion is contained as a counter ion tothe hydrophilic group of the coloring material exhibiting nofluorescence properties.

Further preferred modes of the inks according to the present inventioninclude an ink in which at least one selected from urea and ureaderivatives is contained in addition to the above-described essentialcomponents, an ink in which the urea derivative is not a cycliccompound, and an ink in which the urea derivative is at least oneselected from alkyl derivatives of urea and ethylene oxide and/orpropylene oxide adducts of urea.

Further preferred modes of the inks according to the present inventioninclude an ink in which a compound having a solubility parameter valuebetween the solubility parameter values of the 2 organic compoundsincompatible with each other is used in combination in addition to theabove-described essential components, and an ink which is nonionic in anink system from which the compound exhibiting fluorescence propertiesand/or the coloring material exhibiting fluorescence properties,additives and the other coloring material have been removed.

The inks according to the present invention composed of such componentsas described above preferably have a surface tension of at most 40 mN/m(dyn/cm) and a pH of at least 8. Further, an ink in which an ammoniumion and an alkali metal ion are used in combination as counter ions ofthe coloring material(s) in the ink is preferred. Further, an ink inwhich the excitation maximum wavelength of the ink is smaller than thefluorescence maximum wavelength of the ink is preferred.

As an ink according to another embodiment of the present invention, acompound having a vapor pressure not lower than that of diethyleneglycolis additionally contained in addition to the above-described components,whereby the fluorescence at a colored portion can be retained over along period of time. The mechanism thereof is as described above. Whenone of the 2 organic compounds is a compound having a glycerol group,and the other is a nonionic surfactant, examples of the compound havinga vapor pressure not lower than that of diethyleneglycol include glycolcompounds having a vapor pressure not lower than that of diethyleneglycol. Examples of such glycol compounds include diethylene glycol andethylene glycol.

The ink-jet recording process according to the present invention, inwhich an ink is ejected from an orifice in response to recording signalsto conduct recording on a recording medium, thereby obtaining a recordedarticle features that the above-mentioned ink of a preferred modeaccording to the present invention is used as said ink. The ink-jetrecording process according to the present invention is preferably ofthe type that thermal energy is applied to an ink to be ejected from theorifice to eject droplets of the ink. Preferred modes of the presentinvention include a recorded article obtained by the above-describedink-jet recording process, wherein the fluorescence intensity of arecorded portion formed on wood-free paper has a relatively proportionalrelationship to the water content in the wood-free paper, and a recordedarticle in which the excitation maximum wavelength is smaller than thefluorescence maximum wavelength.

Another preferred mode of the present invention includes a recordingunit comprising an ink container containing the fluorescent ink forink-jet according to the present invention and a head portion forejecting the ink. Preferable examples of the recording unit according tothe present invention include a recording unit in which the head portionhas a construction that thermal energy is applied to the ink to ejectink droplets, a recording unit in which the ink container is formed of apolyolefin, a recording unit in which the ink container has an inkholding member therein, a recording unit in which the ink holding memberis formed of at least one selected from the group consisting ofpolyurethane, cellulose, polyvinyl acetate and polyolefin, and arecording unit in which the ink holding member is composed of a polymerformed by a condensation or polymerization reaction of organiccompound(s).

Further preferable examples of the recording unit according to thepresent invention include a recording unit in which the ink holdingmember is composed of a porous material, a recording unit in which theink holding member has a multi-layer structure, a recording unit inwhich the direction of the multi-layer arrangement of the multi-layerstructure is aligned in an ink discharging direction of the inkcontainer, a recording unit in which the ink holding member is composedof fiber flocculate, a recording unit in which the fiber flocculate isoriented in an ink discharging direction of the ink container, and arecording unit in which the ink holding member has a contact surfacewith the ink container.

A further preferred mode of the present invention includes an inkcartridge comprising an ink container containing the fluorescent inkaccording to the present invention. Preferable examples thereof includean ink cartridge in which the ink container is formed of polyolefin, anink cartridge in which the ink container has an ink holding membertherein, an ink cartridge in which the ink holding member is formed ofat least one selected from the group consisting of polyurethane,cellulose, polyvinyl acetate and polyolefin, and an ink cartridge inwhich the ink holding member is composed of a polymer formed by acondensation or polymerization reaction of organic compound(s).

Further preferable examples of the ink cartridge according to thepresent invention include an ink cartridge in which the ink holdingmember is composed of a porous material, an ink cartridge in which theink holding member has a multi-layer structure, an ink cartridge inwhich the direction of the multi-layer arrangement of the multi-layerstructure is aligned in an ink discharging direction of the inkcontainer, an ink cartridge in which the ink holding member is composedof fiber flocculate, an ink cartridge in which the fiber flocculate isoriented in an ink discharging direction of the ink container, and anink cartridge in which the ink holding member has a contact surface withthe ink container.

A still further preferred mode of the present invention includes anink-jet recording apparatus comprising an ink container containing thefluorescent ink for ink-jet according to the present invention and ahead portion for ejecting the ink. Preferable examples thereof includean ink-jet recording apparatus equipped with the above-mentionedrecording unit according to the present invention.

A yet still further preferred mode of the present invention includes anink-jet recording apparatus equipped with the above-mentioned inkcartridge according to the present invention.

The present invention will hereinafter be described more specifically bythe following Examples and Comparative Examples. Incidentally, alldesignations of “part” or “parts” and “%” as will be used in thefollowing examples mean part or parts by weight and % by weight unlessexpressly noted.

(Ink According to First Embodiment)

EXAMPLES 1 to 8, and COMPARATIVE EXAMPLES 1 to 5

Their corresponding components shown in Tables 1-1 and 1-2 were mixedand thoroughly stirred into solutions or dispersions. The resultantsolutions or dispersions were separately filtered under pressure througha Fluoropore Filter (trade name; product of Sumitomo ElectricIndustries, Ltd.) having a pore size of 0.1 μm, thereby preparing inksaccording to EXAMPLEs and COMPARATIVE EXAMPLEs.

Color under Fluorescent Name of dye Structure daylight colorBrilliant-sulfoflavin FF(C.I. 56205)

Yellow Green toyellowish green Basic YellowHG(C.I. 46040)

Yellow Greenishyellow toyellow Eosine(C.I. 45380)

Red Yellow toorange Rhodamine 6G(C.I. 45160)

Red Yellow toorange Rhodamine B(C.I. 45170)

Pink Orange tored Name of Pigment Structure Lumogen LYellow

Lumogen LBrilliant Yellow

Lumogen LYellow Orange

Lumogen LRed Orange

<Evaluation>

The resultant inks according to EXAMPLES and COMPARATIVE EXAMPLES wereused to evaluate the inks by means of an ink-jet printer BJF 800 (tradename, manufactured by Canon Inc.) in accordance with the followingrespective methods and standards. The results are shown in Table 2.

(Evaluation of Ejection Stability)

Each of the inks was charged in a prescribed amount into an ink tank ofBJF 800 to record English characters and numerals on commerciallyavailable wood-free paper until the ink within the ink tank was used up.After the recording, recorded articles obtained at the first and thelast of the recording were compared with each other to evaluate the inkas to the ejection stability in accordance with the following standard:

-   -   A: No difference was made between both recorded articles;    -   B: Some disorder in quality was observed in the recorded article        obtained at the last of the recording;    -   C: Great disorder in quality was observed in the recorded        article obtained at the last of the recording, and ejection        failure was also marked.        (Evaluation of Stability)

Each of the resultant inks was placed in a laboratory glass dish andleft to stand for 7 days under an environment of 60° C. Thereafter, thecondition of the ink was visually observed to evaluate the ink as to thestability in accordance with the following standard:

-   -   A: Neither precipitate nor separation of ink components was        observed;    -   B: Separation was observed at an interface of the ink;    -   C: Precipitate was observed to a great extent.        (Evaluation of Shelf Stability)

Each of the resultant inks was placed in a glass container, closed andleft to stand for 1 month under an environment of 60° C. Thereafter, theink was left to stand for additional 1 day under an environment ofnormal temperature and then visually observed to evaluate the ink as tothe shelf stability in accordance with the following standard:

-   -   A: None of precipitate, suspended matter and separation of ink        components were observed;    -   B: Precipitate or suspended matter was slightly observed;    -   C: Separation was observed at a gas-liquid interface of the ink;    -   D: Precipitate was observed to a great extent.        (Evaluation of Coloring Ability)

English characters and numerals and a single-color image were recordedon commercially available wood-free paper to visually observe theresultant printed article, thereby evaluating each ink sample as to thecoloring ability in accordance with the following standard:

-   -   A: Bright or clear:    -   B: Not look dull though not bright;    -   C: Look dull.        (Evaluation 1 of Fluorescence Properties)

A solid image was printed at 50% duty on commercially availablewood-free paper under an environment of 23° C. and 50% RH to measurefluorescence intensity of the resulting print at a excitation wavelengthof 260 mm and a emission wavelength of 600 mm by means of a fluorescenceintensity meter, FP-750 (manufactured by Nippon Keiko K.K.) underconditions that the fluorescence intensity of the coloring materialsused in EXAMPLES AND COMPARATIVE EXAMPLES is easiest to measure, therebyevaluating the inks as to the fluorescence properties in accordance withthe following standard:

-   -   A: Fluorescence intensity≧350;    -   B: 350>Fluorescence intensity≧300;    -   C: 200>Fluorescence intensity.        (Evaluation 2 of Fluorescence Properties)

The same measurement as in Evaluation 1 of fluorescence properties wasconducted under low-temperature and low-humidity environment of 15° C.and 10% RH to evaluate the inks in accordance with the same method andstandard as described above. The results are shown in Table 2.

Table 2: Evaluation results of EXAMPLES 1 to 8 and COMPARATIVE EXAMPLES1 to 5

Example Comp. example 1 2 3 4 5 6 7 8 1 2 3 4 5 Ejection stability A A AA A A A A A A A A A Stability A A A A A A A A A A A A A Shelf stabilityA A A A A A A A B B B B B Coloring ability A A A A A A A A C C C C CFluorescence 1 A A A A A A A A C C C C C Fluorescence 2 A A A A A A A AC C C C C(Ink According to Second Embodiment)

EXAMPLES 9 to 16 and COMPARATIVE EXAMPLES 6 to 10

Inks according to respective EXAMPLES and COMPARATIVE EXAMPLES wereprepared in the same manner as in EXAMPLE 1 except that theircorresponding components shown in Tables 3 and 4 were used. The inkswere evaluated in accordance with the same methods and standards as inEXAMPLE 1. With respect to the recorded articles according to EXAMPLES 9to 16 and COMPARATIVE EXAMPLES 6 to 10, change in fluorescenceproperties with time was also observed in accordance with the followingevaluation method and standard.

(Change in Fluorescence Properties with Time)

A solid image was printed at 50% duty on commercially availablewood-free paper to measure fluorescence intensity of the resulting printby means of the fluorescence intensity meter, FP-750. The resultantsolid printed sample was stuck on a wall in a room that was not directlyexposed to sunlight and left to stand for 30 days in a state that afluorescent lighting was turned on. Thereafter, the fluorescenceintensity of the print was measured again. The resultant fluorescenceintensity values were compared to evaluate the ink sample in accordancewith the following standard:

-   -   A: Percent reduction of fluorescence intensity was not more than        5%;    -   B: Percent reduction of fluorescence intensity was not more than        10%;    -   C: Percent reduction of fluorescence intensity was more than        10%.

TABLE 1-1 Ink compositions of EXAMPLEs EXAMPLE 1 2 3 4 5 6 7 8 Compoundexhibiting fluorescence C.I. Acid Red 52 0.2 0.3 0.3 0.2 0.3 0.25 0.40.25 properties or coloring material C.I. Acid Red 92 0.05 exhibitingfluorescence properties C.I. Solvent Green 7 0.1 Coloring materialexhibiting no Exemplified Coloring material 0.4 0.2 0.5 fluorescenceproperties (11) Exemplified Coloring material 0.25 (2) C.I. DirectYellow 86 Compound having glycerol group Glycerol 10 10 8 10 10 8Glycerol (dimer) 5 5 Xylitol 5 Glycol Ethylene glycol Diethylene glycolTriethylene glycol 10 8 10 10 8 Tripropylene glycol 5 SurfactantSurfynol 440 0.1 Surfynol 465 2 2 1.5 1.0 2 0.7 1.5 Surfynol 485Exemplified Compound (V) 1.0 Exemplified Compound (II) 0.5 Sodiumlaurate Other component Urea 8 5 8 Triethanolamine 3 Isopropylalcohol 44 3 4 Purified water Balance

TABLE 1-2 Ink compositions of COMPARATIVE EXAMPLEs COMPARATIVE EXAMPLE 12 3 4 5 Compound exhibiting fluorescence C.I. Acid Red 52 0.3 0.3 0.32.0 0.4 properties or coloring material C.I. Acid Red 92 exhibitingfluorescence properties C.I. Solvent Green 7 Coloring materialexhibiting no Exemplified Coloring material (11) fluorescence propertiesExemplified Coloring material (2) C.I. Direct Yellow 86 Compound havingglycerol group Glycerol 10 10 Glycerol (dimer) Xylitol Glycol Ethyleneglycol 10 Diethylene glycol 10 10 Triethylene glycol 10 10 Tripropyleneglycol Surfactant Surfynol 440 Surfynol 465 2 2 Surfynol 485 ExemplifiedCompound (V) Exemplified Compound (II) Sodium laurate 1 Other componentUrea Triethanolamine 2 Isopropylalcohol 2 4 4 Purified water Balance

TABLE 3 Ink compositions of EXAMPLEs EXAMPLE 9 10 11 12 13 14 15 16Compound exhibiting fluorescence C.I. Acid Red 52 0.2 0.3 0.3 0.2 0.30.25 0.4 0.25 properties or coloring material C.I. Acid Red 92 0.05exhibiting fluorescence properties C.I. Solvent Green 7 0.1 Coloringmaterial exhibiting no Exemplified Coloring material 0.4 0.2 0.5fluorescence properties (11) Exemplified Coloring material 0.25 (2) C.I.Direct Yellow 86 Compound having glycerol group Glycerol 10 10 8 10 10 8Glycerol (dimer) 5 5 Xylitol 5 Glycol Ethylene glycol 10 10 8 8Diethylene glycol 10 10 10 7 Triethylene glycol 10 8 10 10 8Tripropylene glycol 5 Surfactant Surfynol 440 0.1 Surfynol 465 2 2 1.51.0 2 0.7 1.5 Surfynol 485 Exemplified Compound (V) 1.0 ExemplifiedCompound (II) 0.5 Sodium laurate 8 Other component Urea 5 8Triethanolamine 3 Isopropylalcohol 4 4 3 4 Purified water Balance

TABLE 4 Ink compositions of COMPARATIVE EXAMPLEs COMPARATIVE EXAMPLE 1 23 4 5 Compound exhibiting fluorescence C.I. Acid Red 52 0.3 0.3 0.3 2.00.4 properties or coloring material C.I. Acid Red 92 exhibitingfluorescence properties C.I. Solvent Green 7 Coloring materialexhibiting no Exemplified Coloring material (11) fluorescence propertiesExemplified Coloring material (2) C.I. Direct Yellow 86 Compound havingglycerol group Glycerol 10 10 10 Glycerol (dimer) Xylitol GlycolEthylene glycol 10 Diethylene glycol 10 Triethylene glycol 10 10Tripropylene glycol Surfactant Surfynol 440 Surfynol 465 2 2 Surfynol485 Exemplified Compound (V) Exemplified Compound (II) Sodium laurate 1Other component Urea Triethanolamine 2 Isopropylalcohol 2 4 4 4 Purifiedwater Balance

TABLE 5 Example Comp. example 9 10 11 12 13 14 15 16 6 7 8 9 10 Ejectionstability A A A A A A A A A A A A A Stability A A A A A A A A A A A A AShelf stability A A A A A A A A A A A A A Fluorescence 1 A A A A A A A AC A C C C Fluorescence 2 A A A A A A A A C A C C C Change in A A A A A AA A C A C C C fluorescence intensity with time

As described above, according to the present invention, there can beprovided an ink which can provide a recorded article to the recordedportion of which, for example, fluorescence properties important forcolors of the natural kingdom are sufficiently imparted fully makinggood use of the fluorescence properties of the ink, and which therecorded article has high fluorescence intensity and is excellent inprint quality including coloring ability, said ink being capable ofenhancing the stability and reliability of the recorded article, anink-jet recording process using such an ink, a recorded article obtainedby the recording process, and instruments using such an ink. Accordingto an embodiment of the present invention, there can also be provided arecorded article having a fluorescent colored portion the apparentfluorescence intensity of which is hard to be deteriorated with time.

1. A fluorescent ink comprising: (i) first and second organic compoundswhich are incompatible with each other; (ii) at least one of a compoundexhibiting fluorescence properties and a coloring material exhibitingfluorescence properties; and (iii) a liquid medium dissolving ordispersing the components (i) and (ii) therein, wherein the liquidmedium is water, wherein the first and second organic compoundsdissolved or dispersed in the liquid medium cause liquid-liquidseparation owing to evaporation of the water, and wherein the content ofthe component (ii) in the ink is such that concentration quenching doesnot take place.
 2. The ink according to claim 1, wherein the ink is awater-based ink.
 3. The ink according to claim 1, which is applied to arecording medium from an ink applying means wherein there is a gapbetween the ink applying means and the recording medium.
 4. The inkaccording to claim 1, wherein the content of the component (ii) in theink is at most 1.5% by weight based on the total weight of the ink. 5.The ink according to claim 4, wherein the content of the component (ii)in the ink is at most 1.0% by weight based on the total weight of theink.
 6. The ink according to claim 1, wherein the component (ii) iswater-soluble or hydrophilic.
 7. The ink according to claim 1, whereinthe content of the component (ii) in the ink is at least a concentrationsufficient to exhibit the maximum fluorescence intensity in the ink. 8.The ink according to claim 7, wherein the content of the component (ii)in the ink is at least a concentration sufficient to exhibit the maximumfluorescence intensity in a state dissolved in water.
 9. The inkaccording to claim 1, wherein the component (i) dissolves, disperses, ordissolves and disperses the component (ii) therein.
 10. The inkaccording to claim 1, wherein one of the first and second organiccompounds of the component (i) has a solubility parameter value of atleast 15, and the other has a solubility parameter value of at most 13.11. The ink according to claim 1, wherein the first and second organiccompounds of the component (i) are nonpolar compounds.
 12. The inkaccording to claim 1, wherein the first and second organic compounds ofthe component (i) are both water-soluble.
 13. The ink according to claim12, wherein the first and second organic compounds of the component (i)are both liquid.
 14. The ink according to claim 1, wherein one of thefirst and second organic compounds of the component (i) has a glycerolgroup.
 15. The ink according to claim 14, wherein the organic compoundhaving a glycerol group has at least 3 hydroxyl groups.
 16. The inkaccording to claim 14, wherein the organic compound having a glycerolgroup is liquid at normal temperature.
 17. The ink according to claim14, wherein the other of the first and second organic compounds of thecomponent (i) is a nonionic surfactant.
 18. The ink according to claim17, wherein the nonionic surfactant is liquid at normal temperature. 19.The ink according to claim 17, wherein HLB of the nonionic surfactant isat most
 13. 20. The ink according to claim 17, wherein the nonionicsurfactant has a cloud point.
 21. The ink according to claim 19, whereinthe nonionic surfactant is contained in an amount that the nonionicsurfactant is not separated at an interface of an aqueous solution in astate of the aqueous solution.
 22. The ink according to claim 19,wherein the nonionic surfactant is contained in an amount that thenonionic surfactant is not separated at an interface of an aqueoussolution in a state of the aqueous solution, and wherein the nonionicsurfactant is contained in an amount such that in an ink system fromwhich component (ii) has been removed, the nonionic surfactant is notseparated at an interface of the ink.
 23. The ink according to claim 17,wherein the nonionic surfactant has an acetylene group.
 24. The inkaccording to claim 23, wherein the nonionic surfactant has a structurerepresented by the following general formula (I)

wherein A and B are, independently of each other, C_(n)H_(2n+1) (n beingan integer of 1 to 10), and X and Y are, independently of each other, aring-opening ethylene oxide unit and/or a ring-opening propylene oxideunit.
 25. The ink according to claim 17, wherein the nonionic surfactantis contained in a proportion of at least 1% by weight based on the totalweight of the ink.
 26. The ink according to claim 1, which furthercomprises a monohydric alcohol.
 27. The ink according to claim 1, whichfurther comprises a coloring material exhibiting no fluorescenceproperties.
 28. The ink according to claim 27, wherein the coloringmaterial exhibiting no fluorescence properties is a coloring materialhaving water solubility.
 29. The ink according to claim 27, wherein thecoloring material exhibiting no fluorescence properties is a coloringmaterial directly coloring a recording medium.
 30. The ink according toclaim 27, wherein the coloring material exhibiting no fluorescenceproperties is an azo dye.
 31. The ink according to claim 27, wherein thecontent of the coloring material exhibiting no fluorescence propertiesin the ink is not lower than the content of the coloring materialexhibiting fluorescence in the ink.
 32. The ink according to claim 27,wherein the coloring material exhibiting no fluorescence properties hasa carboxyl group or its salt group.
 33. The ink according to claim 27,wherein the counter ion to the hydrophilic group of the coloringmaterial exhibiting no fluorescence properties contains at least oneammonium ion.
 34. The ink according to claim 1, which further comprisesat least one selected from urea and urea derivatives.
 35. The inkaccording to claim 34, wherein the urea derivative is not a cycliccompound.
 36. The ink according to claim 34, wherein the urea derivativeis at least one selected from the group consisting of alkyl derivativesof urea and ethylene oxide and/or propylene oxide adducts of urea. 37.The ink according to claim 1, which further comprises a compound havinga solubility parameter value between the solubility parameter values ofthe two organic compounds incompatible with each other.
 38. The inkaccording to claim 1, which further comprises a compound having a vaporpressure not higher than that of triethylene glycol.
 39. The inkaccording to claim 1, which further comprises a compound having a vaporpressure not lower than that of diethylene glycol.
 40. The ink accordingto claim 39, wherein the compound having a vapor pressure not lower thanthat of diethylene glycol has a solubility parameter between thesolubility parameters of the first and the second organic compoundsincompatible with each other.
 41. The ink according to claim 39 or 40,wherein the compound having a vapor pressure of not lower than that ofdiethylene glycol is at least one of diethylene glycol and ethyleneglycol.
 42. The ink according to claim 1, wherein the ink is adjusted tononionicity in an ink system from which the compound exhibitingfluorescence properties and/or the coloring material exhibitingfluorescence properties, additives and the other coloring material havebeen removed.
 43. The ink according to claim 1, wherein the surfacetension of the ink is at most 40 mN/m (dyn/cm).
 44. The ink according toclaim 1, wherein the ink has the pH of at least
 8. 45. The ink accordingto claim 1, which has a maximum wavelength for excitation and afluorescence maximum wavelength, and the maximum wavelength forexcitation is shorter than the fluorescence maximum wavelength.
 46. Theink according to claim 1, which is an ink for ink-jet recording.
 47. Afluorescent ink comprising: (i) first and second organic compounds whichare incompatible with each other; (ii) at least one of a compoundexhibiting fluorescence properties and a coloring material exhibitingfluorescence properties; and (iii) a liquid medium dissolving ordispersing the components (i) and (ii) therein, wherein the liquidmedium is water, wherein the first and second organic compoundsdissolved or dispersed in the liquid medium cause liquid-liquidseparation owing to evaporation of the water, and wherein the coloringmaterial is C.I. Acid Red 52, and the content of the coloring materialin the ink is at most 0.5% by weight based on the total weight of theink.